--- a/b2g/installer/package-manifest.in
+++ b/b2g/installer/package-manifest.in
@@ -532,18 +532,16 @@
 @BINPATH@/components/satchel.manifest
 @BINPATH@/components/nsFormAutoComplete.js
 @BINPATH@/components/nsFormHistory.js
 @BINPATH@/components/FormHistoryStartup.js
 @BINPATH@/components/nsInputListAutoComplete.js
 @BINPATH@/components/formautofill.manifest
 @BINPATH@/components/FormAutofillContentService.js
 @BINPATH@/components/FormAutofillStartup.js
-@BINPATH@/components/CSSUnprefixingService.js
-@BINPATH@/components/CSSUnprefixingService.manifest
 @BINPATH@/components/contentAreaDropListener.manifest
 @BINPATH@/components/contentAreaDropListener.js
 @BINPATH@/components/messageWakeupService.js
 @BINPATH@/components/messageWakeupService.manifest
 @BINPATH@/components/SettingsManager.js
 @BINPATH@/components/SettingsManager.manifest
 @BINPATH@/components/SettingsService.js
 @BINPATH@/components/SettingsService.manifest

--- a/browser/installer/package-manifest.in
+++ b/browser/installer/package-manifest.in
@@ -471,18 +471,16 @@
 @RESPATH@/components/satchel.manifest
 @RESPATH@/components/nsFormAutoComplete.js
 @RESPATH@/components/nsFormHistory.js
 @RESPATH@/components/FormHistoryStartup.js
 @RESPATH@/components/nsInputListAutoComplete.js
 @RESPATH@/components/formautofill.manifest
 @RESPATH@/components/FormAutofillContentService.js
 @RESPATH@/components/FormAutofillStartup.js
-@RESPATH@/components/CSSUnprefixingService.js
-@RESPATH@/components/CSSUnprefixingService.manifest
 @RESPATH@/components/contentAreaDropListener.manifest
 @RESPATH@/components/contentAreaDropListener.js
 @RESPATH@/browser/components/BrowserProfileMigrators.manifest
 @RESPATH@/browser/components/ProfileMigrator.js
 @RESPATH@/browser/components/ChromeProfileMigrator.js
 @RESPATH@/browser/components/FirefoxProfileMigrator.js
 #ifdef XP_WIN
 @RESPATH@/browser/components/IEProfileMigrator.js

deleted file mode 100644
--- a/layout/style/CSSUnprefixingService.js
+++ /dev/null
@@ -1,157 +0,0 @@
-/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- /
-/* vim: set shiftwidth=2 tabstop=8 autoindent cindent expandtab: */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-/* Implementation of a service that converts certain vendor-prefixed CSS
-   properties to their unprefixed equivalents, for sites on a whitelist. */
-// XXXdholbert whitelist is coming in bug 1132743
-
-"use strict";
-
-const Cc = Components.classes;
-const Ci = Components.interfaces;
-const Cu = Components.utils;
-
-Cu.import("resource://gre/modules/XPCOMUtils.jsm");
-
-function CSSUnprefixingService() {
-}
-
-CSSUnprefixingService.prototype = {
-  // Boilerplate:
-  classID:        Components.ID("{f0729490-e15c-4a2f-a3fb-99e1cc946b42}"),
-  _xpcom_factory: XPCOMUtils.generateSingletonFactory(CSSUnprefixingService),
-  QueryInterface: XPCOMUtils.generateQI([Ci.nsICSSUnprefixingService]),
-
-  // See documentation in nsICSSUnprefixingService.idl
-  generateUnprefixedDeclaration: function(aPropName, aRightHalfOfDecl,
-                                          aUnprefixedDecl /*out*/) {
-
-    // Convert our input strings to lower-case, for easier string-matching.
-    // (NOTE: If we ever need to add support for unprefixing properties that
-    // have case-sensitive parts, then we should do these toLowerCase()
-    // conversions in a more targeted way, to avoid breaking those properties.)
-    aPropName = aPropName.toLowerCase();
-    aRightHalfOfDecl = aRightHalfOfDecl.toLowerCase();
-
-    // We have several groups of supported properties:
-    // FIRST GROUP: Properties that can just be handled as aliases:
-    // ============================================================
-    const propertiesThatAreJustAliases = {
-      "-webkit-background-size":   "background-size",
-      "-webkit-box-flex":          "flex-grow",
-      "-webkit-box-ordinal-group": "order",
-      "-webkit-box-sizing":        "box-sizing",
-      "-webkit-transform":         "transform",
-    };
-
-    let unprefixedPropName = propertiesThatAreJustAliases[aPropName];
-    if (unprefixedPropName !== undefined) {
-      aUnprefixedDecl.value = unprefixedPropName + ":" + aRightHalfOfDecl;
-      return true;
-    }
-
-    // SECOND GROUP: Properties that take a single keyword, where the
-    // unprefixed version takes a different (but analogous) set of keywords:
-    // =====================================================================
-    const propertiesThatNeedKeywordMapping = {
-      "-webkit-box-align" : {
-        unprefixedPropName : "align-items",
-        valueMap : {
-          "start"    : "flex-start",
-          "center"   : "center",
-          "end"      : "flex-end",
-          "baseline" : "baseline",
-          "stretch"  : "stretch"
-        }
-      },
-      "-webkit-box-orient" : {
-        unprefixedPropName : "flex-direction",
-        valueMap : {
-          "horizontal"  : "row",
-          "inline-axis" : "row",
-          "vertical"    : "column",
-          "block-axis"  : "column"
-        }
-      },
-      "-webkit-box-pack" : {
-        unprefixedPropName : "justify-content",
-        valueMap : {
-          "start"    : "flex-start",
-          "center"   : "center",
-          "end"      : "flex-end",
-          "justify"  : "space-between"
-        }
-      },
-    };
-
-    let propInfo = propertiesThatNeedKeywordMapping[aPropName];
-    if (typeof(propInfo) != "undefined") {
-      // Regexp for parsing the right half of a declaration, for keyword-valued
-      // properties. Divides the right half of the declaration into:
-      //  1) any leading whitespace
-      //  2) the property value (one or more alphabetical character or hyphen)
-      //  3) anything after that (e.g. "!important", ";")
-      // Then we can look up the appropriate unprefixed-property value for the
-      // value (part 2), and splice that together with the other parts and with
-      // the unprefixed property-name to make the final declaration.
-      const keywordValuedPropertyRegexp = /^(\s*)([a-z\-]+)(.*)/;
-      let parts = keywordValuedPropertyRegexp.exec(aRightHalfOfDecl);
-      if (!parts) {
-        // Failed to parse a keyword out of aRightHalfOfDecl. (It probably has
-        // no alphabetical characters.)
-        return false;
-      }
-
-      let mappedKeyword = propInfo.valueMap[parts[2]];
-      if (mappedKeyword === undefined) {
-        // We found a keyword in aRightHalfOfDecl, but we don't have a mapping
-        // to an equivalent keyword for the unprefixed version of the property.
-        return false;
-      }
-
-      aUnprefixedDecl.value = propInfo.unprefixedPropName + ":" +
-        parts[1] + // any leading whitespace
-        mappedKeyword +
-        parts[3]; // any trailing text (e.g. !important, semicolon, etc)
-
-      return true;
-    }
-
-    // THIRD GROUP: Properties that may need arbitrary string-replacement:
-    // ===================================================================
-    const propertiesThatNeedStringReplacement = {
-      // "-webkit-transition" takes a multi-part value. If "-webkit-transform"
-      // appears as part of that value, replace it w/ "transform".
-      // And regardless, we unprefix the "-webkit-transition" property-name.
-      // (We could handle other prefixed properties in addition to 'transform'
-      // here, but in practice "-webkit-transform" is the main one that's
-      // likely to be transitioned & that we're concerned about supporting.)
-      "-webkit-transition": {
-        unprefixedPropName : "transition",
-        stringMap : {
-          "-webkit-transform" : "transform",
-        }
-      },
-    };
-
-    propInfo = propertiesThatNeedStringReplacement[aPropName];
-    if (typeof(propInfo) != "undefined") {
-      let newRightHalf = aRightHalfOfDecl;
-      for (let strToReplace in propInfo.stringMap) {
-        let replacement = propInfo.stringMap[strToReplace];
-        newRightHalf = newRightHalf.replace(strToReplace, replacement, "g");
-      }
-      aUnprefixedDecl.value = propInfo.unprefixedPropName + ":" + newRightHalf;
-
-      return true;
-    }
-
-    // No known mapping for property aPropName.
-    return false;
-  },
-};
-
-this.NSGetFactory = XPCOMUtils.generateNSGetFactory([CSSUnprefixingService]);

deleted file mode 100644
--- a/layout/style/CSSUnprefixingService.manifest
+++ /dev/null
@@ -1,2 +0,0 @@
-component {f0729490-e15c-4a2f-a3fb-99e1cc946b42} CSSUnprefixingService.js
-contract @mozilla.org/css-unprefixing-service;1 {f0729490-e15c-4a2f-a3fb-99e1cc946b42}

--- a/layout/style/moz.build
+++ b/layout/style/moz.build
@@ -2,22 +2,16 @@
 # vim: set filetype=python:
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 DIRS += ['xbl-marquee']
 TEST_DIRS += ['test']
 
-XPIDL_SOURCES += [
-    'nsICSSUnprefixingService.idl',
-]
-
-XPIDL_MODULE = 'layout_base'
-
 EXPORTS += [
     'AnimationCommon.h',
     'CounterStyleManager.h',
     'nsAnimationManager.h',
     'nsComputedDOMStylePropertyList.h',
     'nsCSSAnonBoxes.h',
     'nsCSSAnonBoxList.h',
     'nsCSSCounterDescList.h',
@@ -148,21 +142,16 @@ UNIFIED_SOURCES += [
 
 # FontFaceSet.cpp needs to be built separately because it redefines LOG.
 # nsCSSRuleProcessor.cpp needs to be built separately because it uses plarena.h.
 SOURCES += [
     'FontFaceSet.cpp',
     'nsCSSRuleProcessor.cpp',
 ]
 
-EXTRA_COMPONENTS += [
-    'CSSUnprefixingService.js',
-    'CSSUnprefixingService.manifest',
-]
-
 FAIL_ON_WARNINGS = True
 
 MSVC_ENABLE_PGO = True
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 

--- a/layout/style/nsCSSParser.cpp
+++ b/layout/style/nsCSSParser.cpp
@@ -33,17 +33,16 @@
 #include "nsCSSPseudoClasses.h"
 #include "nsCSSPseudoElements.h"
 #include "nsNameSpaceManager.h"
 #include "nsXMLNameSpaceMap.h"
 #include "nsError.h"
 #include "nsIMediaList.h"
 #include "nsStyleUtil.h"
 #include "nsIPrincipal.h"
-#include "nsICSSUnprefixingService.h"
 #include "prprf.h"
 #include "nsContentUtils.h"
 #include "nsAutoPtr.h"
 #include "CSSCalc.h"
 #include "nsMediaFeatures.h"
 #include "nsLayoutUtils.h"
 #include "mozilla/Preferences.h"
 #include "nsRuleData.h"
@@ -52,17 +51,16 @@
 #include "gfxFontFamilyList.h"
 
 using namespace mozilla;
 
 typedef nsCSSProps::KTableValue KTableValue;
 
 // pref-backed bool values (hooked up in nsCSSParser::Startup)
 static bool sOpentypeSVGEnabled;
-static bool sUnprefixingServiceEnabled;
 
 const uint32_t
 nsCSSProps::kParserVariantTable[eCSSProperty_COUNT_no_shorthands] = {
 #define CSS_PROP(name_, id_, method_, flags_, pref_, parsevariant_, kwtable_, \
                  stylestruct_, stylestructoffset_, animtype_)                 \
   parsevariant_,
 #define CSS_PROP_LIST_INCLUDE_LOGICAL
 #include "nsCSSPropList.h"
@@ -413,113 +411,16 @@ protected:
   };
 
   // the caller must hold on to aString until parsing is done
   void InitScanner(nsCSSScanner& aScanner,
                    css::ErrorReporter& aReporter,
                    nsIURI* aSheetURI, nsIURI* aBaseURI,
                    nsIPrincipal* aSheetPrincipal);
   void ReleaseScanner(void);
-
-  /**
-   * This is a RAII class which behaves like an "AutoRestore<>" for our parser
-   * input state. When instantiated, this class saves the current parser input
-   * state (in a CSSParserInputState object), and it restores the parser to
-   * that state when destructed, unless "DoNotRestore()" has been called.
-  */
-  class MOZ_STACK_CLASS nsAutoCSSParserInputStateRestorer {
-    public:
-      explicit nsAutoCSSParserInputStateRestorer(CSSParserImpl* aParser
-                                                 MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
-        : mParser(aParser),
-          mShouldRestore(true)
-      {
-        MOZ_GUARD_OBJECT_NOTIFIER_INIT;
-        mParser->SaveInputState(mSavedState);
-      }
-
-      void DoNotRestore()
-      {
-        mShouldRestore = false;
-      }
-
-      ~nsAutoCSSParserInputStateRestorer()
-      {
-        if (mShouldRestore) {
-          mParser->RestoreSavedInputState(mSavedState);
-        }
-      }
-
-    private:
-      MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
-      CSSParserImpl* mParser;
-      CSSParserInputState mSavedState;
-      bool mShouldRestore;
-  };
-
-  /**
-   * This is a RAII class which creates a temporary nsCSSScanner for the given
-   * string, and reconfigures aParser to use *that* scanner instead of its
-   * existing scanner, until we go out of scope.  (This allows us to rewrite
-   * a portion of a stylesheet using a temporary string, and switch to parsing
-   * that rewritten section, and then resume parsing the original stylesheet.)
-   *
-   * aParser must have a non-null nsCSSScanner (which we'll be temporarily
-   * replacing) and ErrorReporter (which this class will co-opt for the
-   * temporary parser). While we're in scope, we also suppress error reporting,
-   * so it doesn't really matter which reporter we use. We suppress reporting
-   * because this class is only used with CSS that is synthesized & didn't
-   * come directly from an author, and it would be confusing if we reported
-   * syntax errors for CSS that an author didn't provide.
-   *
-   * XXXdholbert we could also change this & report errors, if needed. Might
-   * want to customize the error reporting somehow though.
-   */
-  class MOZ_STACK_CLASS nsAutoScannerChanger {
-    public:
-      nsAutoScannerChanger(CSSParserImpl* aParser,
-                           const nsAString& aStringToScan
-                           MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
-        : mParser(aParser),
-          mOriginalScanner(aParser->mScanner),
-          mStringScanner(aStringToScan, 0),
-          mParserStateRestorer(aParser),
-          mErrorSuppresser(aParser)
-      {
-        MOZ_ASSERT(mOriginalScanner,
-                   "Shouldn't use nsAutoScannerChanger unless we already "
-                   "have a scanner");
-        MOZ_GUARD_OBJECT_NOTIFIER_INIT;
-
-        // Set & setup the new scanner:
-        mParser->mScanner = &mStringScanner;
-        mStringScanner.SetErrorReporter(mParser->mReporter);
-
-        // We might've had push-back on our original scanner (and if we did,
-        // that fact is saved via mParserStateRestorer).  But we don't have
-        // push-back in mStringScanner, so clear that flag.
-        mParser->mHavePushBack = false;
-      }
-
-      ~nsAutoScannerChanger()
-      {
-        // Restore original scanner. All other cleanup is done by RAII members.
-        mParser->mScanner = mOriginalScanner;
-      }
-
-    private:
-      MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
-      CSSParserImpl* mParser;
-      nsCSSScanner *mOriginalScanner;
-      nsCSSScanner mStringScanner;
-      nsAutoCSSParserInputStateRestorer mParserStateRestorer;
-      nsAutoSuppressErrors mErrorSuppresser;
-  };
-
-
   bool IsSVGMode() const {
     return mScanner->IsSVGMode();
   }
 
   /**
    * Saves the current input state, which includes any currently pushed
    * back token, and the current position of the scanner.
    */
@@ -699,49 +600,32 @@ protected:
   // If aStopChar is non-zero, the selector list is done when we hit
   // aStopChar.  Otherwise, it's done when we hit EOF.
   bool ParseSelectorList(nsCSSSelectorList*& aListHead,
                            char16_t aStopChar);
   bool ParseSelectorGroup(nsCSSSelectorList*& aListHead);
   bool ParseSelector(nsCSSSelectorList* aList, char16_t aPrevCombinator);
 
   enum {
-    eParseDeclaration_InBraces           = 1 << 0,
-    eParseDeclaration_AllowImportant     = 1 << 1,
-    // The declaration we're parsing was generated by the CSSUnprefixingService:
-    eParseDeclaration_FromUnprefixingSvc = 1 << 2
+    eParseDeclaration_InBraces       = 1 << 0,
+    eParseDeclaration_AllowImportant = 1 << 1
   };
   enum nsCSSContextType {
     eCSSContext_General,
     eCSSContext_Page
   };
 
   css::Declaration* ParseDeclarationBlock(uint32_t aFlags,
                                           nsCSSContextType aContext = eCSSContext_General);
   bool ParseDeclaration(css::Declaration* aDeclaration,
                         uint32_t aFlags,
                         bool aMustCallValueAppended,
                         bool* aChanged,
                         nsCSSContextType aContext = eCSSContext_General);
 
-  // A "prefix-aware" wrapper for nsCSSKeywords::LookupKeyword().
-  // Use this instead of LookupKeyword() if you might be parsing an unprefixed
-  // property (like "display") for which we emulate a vendor-prefixed value
-  // (like "-webkit-box").
-  nsCSSKeyword LookupKeywordPrefixAware(nsAString& aKeywordStr,
-                                        const KTableValue aKeywordTable[]);
-
-  bool ShouldUseUnprefixingService();
-  bool ParsePropertyWithUnprefixingService(const nsAString& aPropertyName,
-                                           css::Declaration* aDeclaration,
-                                           uint32_t aFlags,
-                                           bool aMustCallValueAppended,
-                                           bool* aChanged,
-                                           nsCSSContextType aContext);
-
   bool ParseProperty(nsCSSProperty aPropID);
   bool ParsePropertyByFunction(nsCSSProperty aPropID);
   bool ParseSingleValueProperty(nsCSSValue& aValue,
                                   nsCSSProperty aPropID);
 
   enum PriorityParsingStatus {
     ePriority_None,
     ePriority_Important,
@@ -1197,22 +1081,16 @@ protected:
   // false.
   bool mInFailingSupportsRule : 1;
 
   // True if we will suppress all parse errors (except unexpected EOFs).
   // This is used to prevent errors for declarations inside a failing
   // @supports rule.
   bool mSuppressErrors : 1;
 
-  // True if we've parsed "display: -webkit-box" as "display: flex" in an
-  // earlier declaration within the current block of declarations, as part of
-  // emulating support for certain -webkit-prefixed properties on certain
-  // sites.
-  bool mDidUnprefixWebkitBoxInEarlierDecl; // not :1 so we can use AutoRestore
-
   // Stack of rule groups; used for @media and such.
   InfallibleTArray<nsRefPtr<css::GroupRule> > mGroupStack;
 
   // During the parsing of a property (which may be a shorthand), the data
   // are stored in |mTempData|.  (It is needed to ensure that parser
   // errors cause the data to be ignored, and to ensure that a
   // non-'!important' declaration does not override an '!important'
   // one.)
@@ -1279,17 +1157,16 @@ CSSParserImpl::CSSParserImpl()
     mUnsafeRulesEnabled(false),
     mIsChromeOrCertifiedApp(false),
     mViewportUnitsEnabled(true),
     mHTMLMediaMode(false),
     mParsingCompoundProperty(false),
     mInSupportsCondition(false),
     mInFailingSupportsRule(false),
     mSuppressErrors(false),
-    mDidUnprefixWebkitBoxInEarlierDecl(false),
     mNextFree(nullptr)
 {
 }
 
 CSSParserImpl::~CSSParserImpl()
 {
   mData.AssertInitialState();
   mTempData.AssertInitialState();
@@ -1508,20 +1385,16 @@ CSSParserImpl::ParseDeclarations(const n
   *aChanged = false;
 
   NS_PRECONDITION(aSheetPrincipal, "Must have principal here!");
 
   nsCSSScanner scanner(aBuffer, 0);
   css::ErrorReporter reporter(scanner, mSheet, mChildLoader, aSheetURI);
   InitScanner(scanner, reporter, aSheetURI, aBaseURI, aSheetPrincipal);
 
-  MOZ_ASSERT(!mDidUnprefixWebkitBoxInEarlierDecl,
-             "Someone forgot to clear the 'did unprefix webkit-box' flag");
-  AutoRestore<bool> autoRestore(mDidUnprefixWebkitBoxInEarlierDecl);
-
   mSection = eCSSSection_General;
 
   mData.AssertInitialState();
   aDeclaration->ClearData();
   // We could check if it was already empty, but...
   *aChanged = true;
 
   for (;;) {
@@ -6156,20 +6029,16 @@ CSSParserImpl::ParseSelector(nsCSSSelect
   return true;
 }
 
 css::Declaration*
 CSSParserImpl::ParseDeclarationBlock(uint32_t aFlags, nsCSSContextType aContext)
 {
   bool checkForBraces = (aFlags & eParseDeclaration_InBraces) != 0;
 
-  MOZ_ASSERT(!mDidUnprefixWebkitBoxInEarlierDecl,
-             "Someone forgot to clear the 'did unprefix webkit-box' flag");
-  AutoRestore<bool> restorer(mDidUnprefixWebkitBoxInEarlierDecl);
-
   if (checkForBraces) {
     if (!ExpectSymbol('{', true)) {
       REPORT_UNEXPECTED_TOKEN(PEBadDeclBlockStart);
       OUTPUT_ERROR();
       return nullptr;
     }
   }
   css::Declaration* declaration = new css::Declaration();
@@ -6567,118 +6436,16 @@ CSSParserImpl::ParseTreePseudoElement(ns
     }
   }
   *aPseudoElementArgs = fakeSelector.mClassList;
   fakeSelector.mClassList = nullptr;
   return true;
 }
 #endif
 
-nsCSSKeyword
-CSSParserImpl::LookupKeywordPrefixAware(nsAString& aKeywordStr,
-                                        const KTableValue aKeywordTable[])
-{
-  nsCSSKeyword keyword = nsCSSKeywords::LookupKeyword(aKeywordStr);
-
-  if (aKeywordTable == nsCSSProps::kDisplayKTable) {
-    if (keyword == eCSSKeyword_UNKNOWN &&
-        ShouldUseUnprefixingService() &&
-        aKeywordStr.EqualsLiteral("-webkit-box")) {
-      // Treat "display: -webkit-box" as "display: flex". In simple scenarios,
-      // they largely behave the same, as long as we use the CSS Unprefixing
-      // Service to also translate the associated properties.
-      mDidUnprefixWebkitBoxInEarlierDecl = true;
-      return eCSSKeyword_flex;
-    }
-
-    // If we've seen "display: -webkit-box" in an earlier declaration and we
-    // tried to unprefix it to emulate support for it, then we have to watch
-    // out for later "display: -moz-box" declarations; they're likely just a
-    // halfhearted attempt at compatibility, and they actually end up stomping
-    // on our emulation of the earlier -webkit-box display-value, via the CSS
-    // cascade. To prevent this problem, we also treat "display: -moz-box" as
-    // "display: flex" (but only if we unprefixed an earlier "-webkit-box").
-    if (mDidUnprefixWebkitBoxInEarlierDecl && keyword == eCSSKeyword__moz_box) {
-      MOZ_ASSERT(ShouldUseUnprefixingService(),
-                 "mDidUnprefixWebkitBoxInEarlierDecl should only be set if "
-                 "we're using the unprefixing service on this site");
-      return eCSSKeyword_flex;
-    }
-  }
-
-  return keyword;
-}
-
-bool
-CSSParserImpl::ShouldUseUnprefixingService()
-{
-  if (!sUnprefixingServiceEnabled) {
-    return false;
-  }
-
-  // XXXdholbert Bug 1132743: Check if stylesheet URI is on fixlist here.
-  return true;
-}
-
-bool
-CSSParserImpl::ParsePropertyWithUnprefixingService(
-  const nsAString& aPropertyName,
-  css::Declaration* aDeclaration,
-  uint32_t aFlags,
-  bool aMustCallValueAppended,
-  bool* aChanged,
-  nsCSSContextType aContext)
-{
-  MOZ_ASSERT(ShouldUseUnprefixingService(),
-             "Caller should've checked ShouldUseUnprefixingService()");
-
-  nsCOMPtr<nsICSSUnprefixingService> unprefixingSvc =
-    do_GetService(NS_CSSUNPREFIXINGSERVICE_CONTRACTID);
-  NS_ENSURE_TRUE(unprefixingSvc, false);
-
-  // Save the state so we can jump back to this spot if our unprefixing fails
-  // (so we can behave as if we didn't even try to unprefix).
-  nsAutoCSSParserInputStateRestorer parserStateBeforeTryingToUnprefix(this);
-
-  // Caller has already parsed the first half of the declaration --
-  // aPropertyName and the ":".  Now, we record the rest of the CSS declaration
-  // (the part after ':') into rightHalfOfDecl.  (This is the property value,
-  // plus anything else up to the end of the declaration -- maybe "!important",
-  // maybe trailing junk characters, maybe a semicolon, maybe a trailing "}".)
-  bool checkForBraces = (aFlags & eParseDeclaration_InBraces) != 0;
-  nsAutoString rightHalfOfDecl;
-  mScanner->StartRecording();
-  SkipDeclaration(checkForBraces);
-  mScanner->StopRecording(rightHalfOfDecl);
-
-  // Try to unprefix:
-  bool success;
-  nsAutoString unprefixedDecl;
-  nsresult rv =
-    unprefixingSvc->GenerateUnprefixedDeclaration(aPropertyName,
-                                                  rightHalfOfDecl,
-                                                  unprefixedDecl, &success);
-  if (NS_FAILED(rv) || !success) {
-    return false;
-  }
-
-  // Attempt to parse the unprefixed declaration:
-  nsAutoScannerChanger scannerChanger(this, unprefixedDecl);
-  success = ParseDeclaration(aDeclaration,
-                             aFlags | eParseDeclaration_FromUnprefixingSvc,
-                             aMustCallValueAppended, aChanged, aContext);
-  if (success) {
-    // We succeeded, so we'll leave the parser pointing at the end of
-    // the declaration; don't restore it to the pre-recording position.
-    parserStateBeforeTryingToUnprefix.DoNotRestore();
-  }
-
-  return success;
-}
-
 //----------------------------------------------------------------------
 
 bool
 CSSParserImpl::ParseDeclaration(css::Declaration* aDeclaration,
                                 uint32_t aFlags,
                                 bool aMustCallValueAppended,
                                 bool* aChanged,
                                 nsCSSContextType aContext)
@@ -6758,29 +6525,17 @@ CSSParserImpl::ParseDeclaration(css::Dec
   } else {
     // Map property name to its ID.
     propID = LookupEnabledProperty(propertyName);
     if (eCSSProperty_UNKNOWN == propID ||
         eCSSPropertyExtra_variable == propID ||
         (aContext == eCSSContext_Page &&
          !nsCSSProps::PropHasFlags(propID,
                                    CSS_PROPERTY_APPLIES_TO_PAGE_RULE))) { // unknown property
-      if (NonMozillaVendorIdentifier(propertyName)) {
-        if (!mInSupportsCondition &&
-            aContext == eCSSContext_General &&
-            !(aFlags & eParseDeclaration_FromUnprefixingSvc) && // no recursion
-            ShouldUseUnprefixingService()) {
-          if (ParsePropertyWithUnprefixingService(propertyName,
-                                                  aDeclaration, aFlags,
-                                                  aMustCallValueAppended,
-                                                  aChanged, aContext)) {
-            return true;
-          }
-        }
-      } else {
+      if (!NonMozillaVendorIdentifier(propertyName)) {
         REPORT_UNEXPECTED_P(PEUnknownProperty, propertyName);
         REPORT_UNEXPECTED(PEDeclDropped);
         OUTPUT_ERROR();
       }
       return false;
     }
     // Then parse the property.
     if (!ParseProperty(propID)) {
@@ -7141,19 +6896,17 @@ CSSParserImpl::ParseVariant(nsCSSValue& 
              "VARIANT_IDENTIFIER_NO_INHERIT");
 
   if (!GetToken(true)) {
     return false;
   }
   nsCSSToken* tk = &mToken;
   if (((aVariantMask & (VARIANT_AHK | VARIANT_NORMAL | VARIANT_NONE | VARIANT_ALL)) != 0) &&
       (eCSSToken_Ident == tk->mType)) {
-    nsCSSKeyword keyword = LookupKeywordPrefixAware(tk->mIdent,
-                                                    aKeywordTable);
-
+    nsCSSKeyword keyword = nsCSSKeywords::LookupKeyword(tk->mIdent);
     if (eCSSKeyword_UNKNOWN < keyword) { // known keyword
       if ((aVariantMask & VARIANT_AUTO) != 0) {
         if (eCSSKeyword_auto == keyword) {
           aValue.SetAutoValue();
           return true;
         }
       }
       if ((aVariantMask & VARIANT_INHERIT) != 0) {
@@ -15302,18 +15055,16 @@ CSSParserImpl::IsValueValidForProperty(c
 
 static CSSParserImpl* gFreeList = nullptr;
 
 /* static */ void
 nsCSSParser::Startup()
 {
   Preferences::AddBoolVarCache(&sOpentypeSVGEnabled,
                                "gfx.font_rendering.opentype_svg.enabled");
-  Preferences::AddBoolVarCache(&sUnprefixingServiceEnabled,
-                               "layout.css.unprefixing-service.enabled");
 }
 
 nsCSSParser::nsCSSParser(mozilla::css::Loader* aLoader,
                          CSSStyleSheet* aSheet)
 {
   CSSParserImpl *impl = gFreeList;
   if (impl) {
     gFreeList = impl->mNextFree;

deleted file mode 100644
--- a/layout/style/nsICSSUnprefixingService.idl
+++ /dev/null
@@ -1,48 +0,0 @@
-/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-/* interface for a service that converts certain vendor-prefixed CSS properties
-   to their unprefixed equivalents */
-
-#include "nsISupports.idl"
-
-[scriptable, uuid(927a5c60-0378-4bcb-a50d-99e6d1fe6063)]
-interface nsICSSUnprefixingService : nsISupports
-{
-  /**
-   * This function helps to convert unsupported vendor-prefixed CSS into
-   * supported unprefixed CSS. Given a vendor-prefixed property name and a
-   * value (or e.g. value + trailing junk like " !important;}"), this function
-   * will attempt to produce an equivalent CSS declaration that uses a
-   * supported unprefixed CSS property.
-   *
-   * @param   aPropName
-   *          The vendor-prefixed property name.
-   *
-   * @param   aRightHalfOfDecl
-   *          Everything after the ":" in the CSS declaration. This includes
-   *          the property's value, along with possibly some leading whitespace
-   *          and trailing text like "!important", and possibly a ';' and/or
-   *          '}' (along with any other bogus text the author happens to
-   *          include before those, which will probably make the decl invalid).
-   *
-   * @param   aUnprefixedDecl[out]
-   *          The resulting unprefixed declaration, if we return true.
-   *
-   * @return true if we were able to unprefix -- i.e. if we were able to
-   *         convert the property to a known unprefixed equivalent, and we also
-   *         performed any known-to-be-necessary fixup on the value, and we put
-   *         the result in aUnprefixedDecl.
-   *         Otherwise, this function returns false.
-   */
-  boolean generateUnprefixedDeclaration(in AString aPropName,
-                                        in AString aRightHalfOfDecl,
-                                        out AString aUnprefixedDecl);
-};
-
-%{C++
-#define NS_CSSUNPREFIXINGSERVICE_CONTRACTID \
-    "@mozilla.org/css-unprefixing-service;1"
-%}

--- a/layout/style/test/mochitest.ini
+++ b/layout/style/test/mochitest.ini
@@ -218,17 +218,16 @@ skip-if = buildapp == 'b2g' || toolkit =
 [test_transitions_step_functions.html]
 [test_transitions_dynamic_changes.html]
 [test_transitions_bug537151.html]
 [test_unclosed_parentheses.html]
 [test_units_angle.html]
 [test_units_frequency.html]
 [test_units_length.html]
 [test_units_time.html]
-[test_unprefixing_service.html]
 [test_value_cloning.html]
 skip-if = (toolkit == 'gonk' && debug) || toolkit == 'android' #bug 775227 #debug-only failure; timed out
 [test_value_computation.html]
 skip-if = (toolkit == 'gonk' && debug) || toolkit == 'android' #debug-only failure
 [test_value_storage.html]
 skip-if = (toolkit == 'gonk' && debug) #debug-only failure
 [test_variable_serialization_computed.html]
 [test_variable_serialization_specified.html]

deleted file mode 100644
--- a/layout/style/test/test_unprefixing_service.html
+++ /dev/null
@@ -1,240 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<!--
-https://bugzilla.mozilla.org/show_bug.cgi?id=1107378
--->
-<head>
-  <meta charset="utf-8">
-  <title>Test for Bug 1107378</title>
-  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
-  <script type="text/javascript" src="property_database.js"></script>
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
-</head>
-<body>
-<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1107378">Mozilla Bug 1107378</a>
-<div id="display">
-  <div id="content">
-  </div>
-</div>
-<pre id="test">
-<script type="application/javascript;version=1.7">
-"use strict";
-
-/** Test for the CSS Unprefixing Service (Bug 1107378) **/
-
-function getComputedStyleWrapper(elem, prop)
-{
-  return window.getComputedStyle(elem, null).getPropertyValue(prop);
-}
-
-const gTestcases = [
-  { decl:  "-webkit-box-flex:5",
-    targetPropName: "flex-grow",
-    targetPropVal:  "5" },
-
-  /* If author happens to specify modern flexbox style after prefixed style,
-     make sure the modern stuff is preserved. */
-  { decl:  "-webkit-box-flex:4;flex-grow:6",
-    targetPropName: "flex-grow",
-    targetPropVal:  "6" },
-
-  /* Tests for handling !important: */
-  { decl:  "-webkit-box-flex:3!important;",
-    targetPropName: "flex-grow",
-    targetPropVal:  "3" },
-  { decl:  "-webkit-box-flex:2!important;flex-grow:1",
-    targetPropName: "flex-grow",
-    targetPropVal:  "2" },
-
-  { decl:  "-webkit-box-flex:1!important bogusText;",
-    targetPropName: "flex-grow"
-    /* invalid syntax --> no target prop-val. */
-  },
-
-  // Make sure we handle weird capitalization in property & value, too:
-  { decl: "-WEBKIT-BoX-aLign: baSELine",
-    targetPropName: "align-items",
-    targetPropVal:  "baseline" },
-
-  { decl: "display:-webkit-box",
-    targetPropName: "display",
-    targetPropVal:  "flex" },
-
-  { decl: "display:-webkit-box; display:-moz-box;",
-    targetPropName: "display",
-    targetPropVal:  "flex" },
-
-  { decl: "display:-webkit-foobar; display:-moz-box;",
-    targetPropName: "display",
-    targetPropVal:  "-moz-box" },
-
-  // -webkit-box-align: baseline | center | end      | start      | stretch
-  // ...maps to:
-  // align-items:       baseline | center | flex-end | flex-start | stretch
-  { decl: "-webkit-box-align: baseline",
-    targetPropName: "align-items",
-    targetPropVal:  "baseline" },
-  { decl: "-webkit-box-align: center",
-    targetPropName: "align-items",
-    targetPropVal:  "center" },
-  { decl: "-webkit-box-align: end",
-    targetPropName: "align-items",
-    targetPropVal:  "flex-end" },
-  { decl: "-webkit-box-align: start",
-    targetPropName: "align-items",
-    targetPropVal:  "flex-start" },
-  { decl: "-webkit-box-align: stretch",
-    targetPropName: "align-items",
-    targetPropVal:  "stretch" },
-
-  // -webkit-box-direction is not supported, because it's unused & would be
-  // complicated to support. See note in CSSUnprefixingService.js for more.
-
-  // -webkit-box-ordinal-group: <number> maps directly to "order".
-  { decl:  "-webkit-box-ordinal-group: 2",
-    targetPropName: "order",
-    targetPropVal:  "2" },
-  { decl:  "-webkit-box-ordinal-group: 6000",
-    targetPropName: "order",
-    targetPropVal:  "6000" },
-
-  // -webkit-box-orient: horizontal | inline-axis | vertical | block-axis
-  // ...maps to:
-  // flex-direction:     row        | row         | column   | column
-  { decl: "-webkit-box-orient: horizontal",
-    targetPropName: "flex-direction",
-    targetPropVal:  "row" },
-  { decl: "-webkit-box-orient: inline-axis",
-    targetPropName: "flex-direction",
-    targetPropVal:  "row" },
-  { decl: "-webkit-box-orient: vertical",
-    targetPropName: "flex-direction",
-    targetPropVal:  "column" },
-  { decl: "-webkit-box-orient: block-axis",
-    targetPropName: "flex-direction",
-    targetPropVal:  "column" },
-
-  // -webkit-box-pack: start     | center | end      | justify
-  // ... maps to:
-  // justify-content: flex-start | center | flex-end | space-between
-  { decl: "-webkit-box-pack: start",
-    targetPropName: "justify-content",
-    targetPropVal:  "flex-start" },
-  { decl: "-webkit-box-pack: center",
-    targetPropName: "justify-content",
-    targetPropVal:  "center" },
-  { decl: "-webkit-box-pack: end",
-    targetPropName: "justify-content",
-    targetPropVal:  "flex-end" },
-  { decl: "-webkit-box-pack: justify",
-    targetPropName: "justify-content",
-    targetPropVal:  "space-between" },
-
-  // -webkit-transform: <transform> maps directly to "transform"
-  { decl: "-webkit-transform: matrix(1, 2, 3, 4, 5, 6)",
-    targetPropName: "transform",
-    targetPropVal:  "matrix(1, 2, 3, 4, 5, 6)" },
-
-  // -webkit-transition: <property> maps directly to "transition"
-  { decl: "-webkit-transition: width 1s linear 2s",
-    targetPropName: "transition",
-    targetPropVal:  "width 1s linear 2s" },
-
-  // -webkit-transition **with** -webkit-prefixed property in value.
-  { decl: "-webkit-transition: -webkit-transform 1s linear 2s",
-    targetPropName: "transition",
-    targetPropVal:  "transform 1s linear 2s" },
-  // (Re-test to check that it sets the "transition-property" subproperty.)
-  { decl: "-webkit-transition: -webkit-transform 1s linear 2s",
-    targetPropName: "transition-property",
-    targetPropVal:  "transform" },
-
-  // Same as previous test, except with "-webkit-transform" in the
-  // middle of the value instead of at the beginning (still valid):
-  { decl: "-webkit-transition: 1s -webkit-transform linear 2s",
-    targetPropName: "transition",
-    targetPropVal:  "transform 1s linear 2s" },
-  { decl: "-webkit-transition: 1s -webkit-transform linear 2s",
-    targetPropName: "transition-property",
-    targetPropVal:  "transform" },
-];
-
-// The main test function.
-// aFlexboxTestcase is an entry from the list in flexbox_layout_testcases.js
-function runOneTest(aTestcase)
-{
-  let elem = document.getElementById("content");
-
-  let expectedValueInDOMStyle;
-  let expectedValueInComputedStyle;
-  if (typeof(aTestcase.targetPropVal) == 'undefined') {
-    expectedValueInDOMStyle = '';
-    expectedValueInComputedStyle = // initial computed style:
-      getComputedStyleWrapper(elem, aTestcase.targetPropName);
-  } else {
-    expectedValueInDOMStyle = aTestcase.targetPropVal;
-    expectedValueInComputedStyle = aTestcase.targetPropVal;
-  }
-
-  elem.setAttribute("style", aTestcase.decl);
-
-  // Check specified style for fixup:
-  is(elem.style[aTestcase.targetPropName], expectedValueInDOMStyle,
-     "Checking if unprefixing service produced expected result " +
-     "in elem.style['" + aTestcase.targetPropName + "'] " +
-     "when given decl '" + aTestcase.decl + "'");
-
-  // Check computed style for fixup:
-  // (only for longhand properties; shorthands aren't in computed style)
-  if (gCSSProperties[aTestcase.targetPropName].type == CSS_TYPE_LONGHAND) {
-    let computedValue = getComputedStyleWrapper(elem, aTestcase.targetPropName);
-    is(computedValue, expectedValueInComputedStyle,
-       "Checking if unprefixing service produced expected result " +
-       "in computed value of property '" +  aTestcase.targetPropName + "' " +
-       "when given decl '" + aTestcase.decl + "'");
-  }
-
-  elem.setAttribute("style", "");
-}
-
-function testWithUnprefixingDisabled()
-{
-  // Sanity-check that -webkit-prefixed properties are rejected, when
-  // pref is disabled:
-  let elem = document.getElementById("content");
-  let initialFlexGrow = getComputedStyleWrapper(elem, "flex-grow");
-  elem.setAttribute("style", "-webkit-box-flex:5");
-  is(getComputedStyleWrapper(elem, "flex-grow"), initialFlexGrow,
-     "-webkit-box-flex shouldn't affect 'flex-grow' " +
-     "when unprefixing pref is disabled");
-
-  let initialDisplay = getComputedStyleWrapper(elem, "display");
-  elem.setAttribute("style", "display:-webkit-box");
-  is(getComputedStyleWrapper(elem, "display"), initialDisplay,
-     "-webkit-box-flex shouldn't affect 'display' " +
-     "when unprefixing pref is disabled");
-}
-
-function testWithUnprefixingEnabled()
-{
-  gTestcases.forEach(runOneTest);
-  SimpleTest.finish();
-}
-
-SimpleTest.waitForExplicitFinish();
-
-// First, test with unprefixing disabled (by default for now):
-testWithUnprefixingDisabled();
-
-// ...and then test with it enabled.
-// XXXdholbert in bug 1132743, we'll be restricting unprefixing to only happen
-// on a "fixlist" of domains. We'll need to run this test from a predetermined
-// fake mochitest-domain, and include that domain in the "fixlist".
-SpecialPowers.pushPrefEnv(
-  { set: [["layout.css.unprefixing-service.enabled", true]] },
-  testWithUnprefixingEnabled);
-
-</script>
-</pre>
-</body>
-</html>

--- a/mobile/android/installer/package-manifest.in
+++ b/mobile/android/installer/package-manifest.in
@@ -386,18 +386,16 @@
 @BINPATH@/components/satchel.manifest
 @BINPATH@/components/nsFormAutoComplete.js
 @BINPATH@/components/nsFormHistory.js
 @BINPATH@/components/FormHistoryStartup.js
 @BINPATH@/components/nsInputListAutoComplete.js
 @BINPATH@/components/formautofill.manifest
 @BINPATH@/components/FormAutofillContentService.js
 @BINPATH@/components/FormAutofillStartup.js
-@BINPATH@/components/CSSUnprefixingService.js
-@BINPATH@/components/CSSUnprefixingService.manifest
 @BINPATH@/components/contentAreaDropListener.manifest
 @BINPATH@/components/contentAreaDropListener.js
 @BINPATH@/components/messageWakeupService.js
 @BINPATH@/components/messageWakeupService.manifest
 #ifdef MOZ_ENABLE_DBUS
 @BINPATH@/components/@DLL_PREFIX@dbusservice@DLL_SUFFIX@
 #endif
 @BINPATH@/components/nsINIProcessor.manifest

--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -2149,20 +2149,16 @@ pref("layout.css.image-orientation.enabl
 // Are sets of prefixed properties supported?
 pref("layout.css.prefixes.border-image", true);
 pref("layout.css.prefixes.transforms", true);
 pref("layout.css.prefixes.transitions", true);
 pref("layout.css.prefixes.animations", true);
 pref("layout.css.prefixes.box-sizing", true);
 pref("layout.css.prefixes.font-features", true);
 
-// Is the CSS Unprefixing Service enabled? (This service emulates support
-// for certain vendor-prefixed properties & values, for sites on a "fixlist".)
-pref("layout.css.unprefixing-service.enabled", false);
-
 // Is support for the :scope selector enabled?
 pref("layout.css.scope-pseudo.enabled", true);
 
 // Is support for background-blend-mode enabled?
 pref("layout.css.background-blend-mode.enabled", true);
 
 // Is support for CSS vertical text enabled?
 pref("layout.css.vertical-text.enabled", false);