--- a/dom/base/ResponsiveImageSelector.cpp
+++ b/dom/base/ResponsiveImageSelector.cpp
@@ -11,20 +11,16 @@
 #include "nsPresContext.h"
 
 #include "nsCSSParser.h"
 #include "nsCSSProps.h"
 #include "nsIMediaList.h"
 #include "nsRuleNode.h"
 #include "nsRuleData.h"
 
-// For IsPictureEnabled() -- the candidate parser needs to be aware of sizes
-// support being enabled
-#include "HTMLPictureElement.h"
-
 using namespace mozilla;
 using namespace mozilla::dom;
 
 namespace mozilla {
 namespace dom {
 
 NS_IMPL_CYCLE_COLLECTION(ResponsiveImageSelector, mOwnerNode)
 
@@ -552,18 +548,17 @@ ResponsiveImageDescriptors::AddDescripto
   aDescriptor.EndReading(descType);
   descType--;
   const nsDependentSubstring& valueStr = Substring(descStart, descType);
   if (*descType == char16_t('w')) {
     int32_t possibleWidth;
     // If the value is not a valid non-negative integer, it doesn't match this
     // descriptor, fall through.
     if (ParseInteger(valueStr, possibleWidth) && possibleWidth >= 0) {
-      if (possibleWidth != 0 && HTMLPictureElement::IsPictureEnabled() &&
-          mWidth.isNothing() && mDensity.isNothing()) {
+      if (possibleWidth != 0 && mWidth.isNothing() && mDensity.isNothing()) {
         mWidth.emplace(possibleWidth);
       } else {
         // Valid width descriptor, but width or density were already seen, sizes
         // support isn't enabled, or it parsed to 0, which is an error per spec
         mInvalid = true;
       }
 
       return;

--- a/dom/html/HTMLImageElement.cpp
+++ b/dom/html/HTMLImageElement.cpp
@@ -45,22 +45,18 @@
 
 #include "nsIDOMHTMLMapElement.h"
 #include "mozilla/EventDispatcher.h"
 #include "mozilla/EventStates.h"
 #include "mozilla/net/ReferrerPolicy.h"
 
 #include "nsLayoutUtils.h"
 
-#include "mozilla/Preferences.h"
-
 using namespace mozilla::net;
 
-static const char *kPrefSrcsetEnabled = "dom.image.srcset.enabled";
-
 NS_IMPL_NS_NEW_HTML_ELEMENT(Image)
 
 #ifdef DEBUG
 // Is aSubject a previous sibling of aNode.
 static bool IsPreviousSibling(nsINode *aSubject, nsINode *aNode)
 {
   if (aSubject == aNode) {
     return false;
@@ -165,29 +161,19 @@ NS_IMPL_INT_ATTR(HTMLImageElement, Vspac
 
 bool
 HTMLImageElement::IsInteractiveHTMLContent(bool aIgnoreTabindex) const
 {
   return HasAttr(kNameSpaceID_None, nsGkAtoms::usemap) ||
           nsGenericHTMLElement::IsInteractiveHTMLContent(aIgnoreTabindex);
 }
 
-bool
-HTMLImageElement::IsSrcsetEnabled()
-{
-  return Preferences::GetBool(kPrefSrcsetEnabled, false);
-}
-
 nsresult
 HTMLImageElement::GetCurrentSrc(nsAString& aValue)
 {
-  if (!IsSrcsetEnabled()) {
-    return NS_ERROR_FAILURE;
-  }
-
   nsCOMPtr<nsIURI> currentURI;
   GetCurrentURI(getter_AddRefs(currentURI));
   if (currentURI) {
     nsAutoCString spec;
     currentURI->GetSpec(spec);
     CopyUTF8toUTF16(spec, aValue);
   } else {
     SetDOMStringToNull(aValue);
@@ -428,22 +414,20 @@ HTMLImageElement::AfterSetAttr(int32_t a
         mResponsiveSelector->SetDefaultSource(NullString());
       }
       QueueImageLoadTask(true);
     } else {
       // Bug 1076583 - We still behave synchronously in the non-responsive case
       CancelImageRequests(aNotify);
     }
   } else if (aName == nsGkAtoms::srcset &&
-             aNameSpaceID == kNameSpaceID_None &&
-             IsSrcsetEnabled()) {
+             aNameSpaceID == kNameSpaceID_None) {
     PictureSourceSrcsetChanged(this, attrVal.String(), aNotify);
   } else if (aName == nsGkAtoms::sizes &&
-             aNameSpaceID == kNameSpaceID_None &&
-             HTMLPictureElement::IsPictureEnabled()) {
+             aNameSpaceID == kNameSpaceID_None) {
     PictureSourceSizesChanged(this, attrVal.String(), aNotify);
   }
 
   return nsGenericHTMLElement::AfterSetAttr(aNameSpaceID, aName,
                                             aValue, aNotify);
 }
 
 nsresult
@@ -924,24 +908,20 @@ HTMLImageElement::QueueImageLoadTask(boo
   // queued event, and so earlier tasks are implicitly canceled.
   mPendingImageLoadTask = task;
   nsContentUtils::RunInStableState(task.forget());
 }
 
 bool
 HTMLImageElement::HaveSrcsetOrInPicture()
 {
-  if (IsSrcsetEnabled() && HasAttr(kNameSpaceID_None, nsGkAtoms::srcset)) {
+  if (HasAttr(kNameSpaceID_None, nsGkAtoms::srcset)) {
     return true;
   }
 
-  if (!HTMLPictureElement::IsPictureEnabled()) {
-    return false;
-  }
-
   Element *parent = nsINode::GetParentElement();
   return (parent && parent->IsHTMLElement(nsGkAtoms::picture));
 }
 
 bool
 HTMLImageElement::InResponsiveMode()
 {
   // When we lose srcset or leave a <picture> element, the fallback to img.src
@@ -1022,24 +1002,18 @@ HTMLImageElement::LoadSelectedImage(bool
   return rv;
 }
 
 void
 HTMLImageElement::PictureSourceSrcsetChanged(nsIContent *aSourceNode,
                                              const nsAString& aNewValue,
                                              bool aNotify)
 {
-  bool isSelf = aSourceNode == this;
-
-  if (!IsSrcsetEnabled() ||
-      (!isSelf && !HTMLPictureElement::IsPictureEnabled())) {
-    return;
-  }
-
-  MOZ_ASSERT(isSelf || IsPreviousSibling(aSourceNode, this),
+  MOZ_ASSERT(aSourceNode == this ||
+             IsPreviousSibling(aSourceNode, this),
              "Should not be getting notifications for non-previous-siblings");
 
   nsIContent *currentSrc =
     mResponsiveSelector ? mResponsiveSelector->Content() : nullptr;
 
   if (aSourceNode == currentSrc) {
     // We're currently using this node as our responsive selector
     // source.
@@ -1059,20 +1033,16 @@ HTMLImageElement::PictureSourceSrcsetCha
   QueueImageLoadTask(true);
 }
 
 void
 HTMLImageElement::PictureSourceSizesChanged(nsIContent *aSourceNode,
                                             const nsAString& aNewValue,
                                             bool aNotify)
 {
-  if (!HTMLPictureElement::IsPictureEnabled()) {
-    return;
-  }
-
   MOZ_ASSERT(aSourceNode == this ||
              IsPreviousSibling(aSourceNode, this),
              "Should not be getting notifications for non-previous-siblings");
 
   nsIContent *currentSrc =
     mResponsiveSelector ? mResponsiveSelector->Content() : nullptr;
 
   if (aSourceNode == currentSrc) {
@@ -1085,70 +1055,52 @@ HTMLImageElement::PictureSourceSizesChan
   // we are not using this source.
   QueueImageLoadTask(true);
 }
 
 void
 HTMLImageElement::PictureSourceMediaOrTypeChanged(nsIContent *aSourceNode,
                                                   bool aNotify)
 {
-  if (!HTMLPictureElement::IsPictureEnabled()) {
-    return;
-  }
-
   MOZ_ASSERT(IsPreviousSibling(aSourceNode, this),
              "Should not be getting notifications for non-previous-siblings");
 
   // This always triggers the image update steps per the spec, even if
   // we are not switching to/from this source
   QueueImageLoadTask(true);
 }
 
 void
 HTMLImageElement::PictureSourceAdded(nsIContent *aSourceNode)
 {
-  if (!HTMLPictureElement::IsPictureEnabled()) {
-    return;
-  }
-
   MOZ_ASSERT(aSourceNode == this ||
              IsPreviousSibling(aSourceNode, this),
              "Should not be getting notifications for non-previous-siblings");
 
   QueueImageLoadTask(true);
 }
 
 void
 HTMLImageElement::PictureSourceRemoved(nsIContent *aSourceNode)
 {
-  if (!HTMLPictureElement::IsPictureEnabled()) {
-    return;
-  }
-
   MOZ_ASSERT(aSourceNode == this ||
              IsPreviousSibling(aSourceNode, this),
              "Should not be getting notifications for non-previous-siblings");
 
   QueueImageLoadTask(true);
 }
 
 bool
 HTMLImageElement::UpdateResponsiveSource()
 {
   bool hadSelector = !!mResponsiveSelector;
 
-  if (!IsSrcsetEnabled()) {
-    mResponsiveSelector = nullptr;
-    return hadSelector;
-  }
-
   nsIContent *currentSource =
     mResponsiveSelector ? mResponsiveSelector->Content() : nullptr;
-  bool pictureEnabled = HTMLPictureElement::IsPictureEnabled();
-  Element *parent = pictureEnabled ? nsINode::GetParentElement() : nullptr;
+  Element *parent = nsINode::GetParentElement();
 
   nsINode *candidateSource = nullptr;
   if (parent && parent->IsHTMLElement(nsGkAtoms::picture)) {
     // Walk source nodes previous to ourselves
     candidateSource = parent->GetFirstChild();
   } else {
     candidateSource = this;
   }
@@ -1226,17 +1178,16 @@ HTMLImageElement::SupportedPictureSource
 bool
 HTMLImageElement::SourceElementMatches(nsIContent* aSourceNode)
 {
   MOZ_ASSERT(aSourceNode->IsHTMLElement(nsGkAtoms::source));
 
   DebugOnly<Element *> parent(nsINode::GetParentElement());
   MOZ_ASSERT(parent && parent->IsHTMLElement(nsGkAtoms::picture));
   MOZ_ASSERT(IsPreviousSibling(aSourceNode, this));
-  MOZ_ASSERT(HTMLPictureElement::IsPictureEnabled());
 
   // Check media and type
   HTMLSourceElement *src = static_cast<HTMLSourceElement*>(aSourceNode);
   if (!src->MatchesCurrentMedia()) {
     return false;
   }
 
   nsAutoString type;
@@ -1248,21 +1199,16 @@ HTMLImageElement::SourceElementMatches(n
   return true;
 }
 
 bool
 HTMLImageElement::TryCreateResponsiveSelector(nsIContent *aSourceNode,
                                               const nsAString *aSrcset,
                                               const nsAString *aSizes)
 {
-  if (!IsSrcsetEnabled()) {
-    return false;
-  }
-
-  bool pictureEnabled = HTMLPictureElement::IsPictureEnabled();
   // Skip if this is not a <source> with matching media query
   bool isSourceTag = aSourceNode->IsHTMLElement(nsGkAtoms::source);
   if (isSourceTag) {
     if (!SourceElementMatches(aSourceNode)) {
       return false;
     }
   } else if (aSourceNode->IsHTMLElement(nsGkAtoms::img)) {
     // Otherwise this is the <img> tag itself
@@ -1285,19 +1231,19 @@ HTMLImageElement::TryCreateResponsiveSel
 
   // Try to parse
   RefPtr<ResponsiveImageSelector> sel = new ResponsiveImageSelector(aSourceNode);
   if (!sel->SetCandidatesFromSourceSet(srcset)) {
     // No possible candidates, don't need to bother parsing sizes
     return false;
   }
 
-  if (pictureEnabled && aSizes) {
+  if (aSizes) {
     sel->SetSizesFromDescriptor(*aSizes);
-  } else if (pictureEnabled) {
+  } else {
     nsAutoString sizes;
     aSourceNode->GetAttr(kNameSpaceID_None, nsGkAtoms::sizes, sizes);
     sel->SetSizesFromDescriptor(sizes);
   }
 
   // If this is the <img> tag, also pull in src as the default source
   if (!isSourceTag) {
     MOZ_ASSERT(aSourceNode == this);
@@ -1321,22 +1267,17 @@ HTMLImageElement::SelectSourceForTagWith
                                               const nsAString& aMediaAttr,
                                               nsAString& aResult)
 {
   MOZ_ASSERT(aIsSourceTag || (aTypeAttr.IsEmpty() && aMediaAttr.IsEmpty()),
              "Passing type or media attrs makes no sense without aIsSourceTag");
   MOZ_ASSERT(!aIsSourceTag || aSrcAttr.IsEmpty(),
              "Passing aSrcAttr makes no sense with aIsSourceTag set");
 
-  bool pictureEnabled = HTMLPictureElement::IsPictureEnabled();
-  if (aIsSourceTag && !pictureEnabled) {
-    return false;
-  }
-
-  if (!IsSrcsetEnabled() || aSrcsetAttr.IsEmpty()) {
+  if (aSrcsetAttr.IsEmpty()) {
     if (!aIsSourceTag) {
       // For an <img> with no srcset, we would always select the src attr.
       aResult.Assign(aSrcAttr);
       return true;
     }
     // Otherwise, a <source> without srcset is never selected
     return false;
   }
@@ -1350,17 +1291,17 @@ HTMLImageElement::SelectSourceForTagWith
     return false;
   }
 
   // Using srcset or picture <source>, build a responsive selector for this tag.
   RefPtr<ResponsiveImageSelector> sel =
     new ResponsiveImageSelector(aDocument);
 
   sel->SetCandidatesFromSourceSet(aSrcsetAttr);
-  if (pictureEnabled && !aSizesAttr.IsEmpty()) {
+  if (!aSizesAttr.IsEmpty()) {
     sel->SetSizesFromDescriptor(aSizesAttr);
   }
   if (!aIsSourceTag) {
     sel->SetDefaultSource(aSrcAttr);
   }
 
   if (sel->GetSelectedImageURLSpec(aResult)) {
     return true;

--- a/dom/html/HTMLImageElement.h
+++ b/dom/html/HTMLImageElement.h
@@ -10,19 +10,16 @@
 #include "mozilla/Attributes.h"
 #include "nsGenericHTMLElement.h"
 #include "nsImageLoadingContent.h"
 #include "nsIDOMHTMLImageElement.h"
 #include "imgRequestProxy.h"
 #include "Units.h"
 #include "nsCycleCollectionParticipant.h"
 
-// Only needed for IsPictureEnabled()
-#include "mozilla/dom/HTMLPictureElement.h"
-
 namespace mozilla {
 class EventChainPreVisitor;
 namespace dom {
 
 class ImageLoadTask;
 
 class ResponsiveImageSelector;
 class HTMLImageElement final : public nsGenericHTMLElement,
@@ -92,18 +89,16 @@ public:
 
   virtual EventStates IntrinsicState() const override;
   virtual nsresult Clone(mozilla::dom::NodeInfo *aNodeInfo, nsINode **aResult) const override;
 
   nsresult CopyInnerTo(Element* aDest);
 
   void MaybeLoadImage();
 
-  static bool IsSrcsetEnabled();
-
   bool IsMap()
   {
     return GetBoolAttr(nsGkAtoms::ismap);
   }
   void SetIsMap(bool aIsMap, ErrorResult& aError)
   {
     SetHTMLBoolAttr(nsGkAtoms::ismap, aIsMap, aError);
   }

--- a/dom/html/HTMLPictureElement.cpp
+++ b/dom/html/HTMLPictureElement.cpp
@@ -3,28 +3,21 @@
 /* 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/. */
 
 #include "mozilla/dom/HTMLPictureElement.h"
 #include "mozilla/dom/HTMLPictureElementBinding.h"
 #include "mozilla/dom/HTMLImageElement.h"
 
-#include "mozilla/Preferences.h"
-static const char *kPrefPictureEnabled = "dom.image.picture.enabled";
-
 // Expand NS_IMPL_NS_NEW_HTML_ELEMENT(Picture) to add pref check.
 nsGenericHTMLElement*
 NS_NewHTMLPictureElement(already_AddRefed<mozilla::dom::NodeInfo>&& aNodeInfo,
                          mozilla::dom::FromParser aFromParser)
 {
-  if (!mozilla::dom::HTMLPictureElement::IsPictureEnabled()) {
-    return new mozilla::dom::HTMLUnknownElement(aNodeInfo);
-  }
-
   return new mozilla::dom::HTMLPictureElement(aNodeInfo);
 }
 
 namespace mozilla {
 namespace dom {
 
 HTMLPictureElement::HTMLPictureElement(already_AddRefed<mozilla::dom::NodeInfo>& aNodeInfo)
   : nsGenericHTMLElement(aNodeInfo)
@@ -90,23 +83,16 @@ HTMLPictureElement::InsertChildAt(nsICon
         }
       } while ( (nextSibling = nextSibling->GetNextSibling()) );
     }
   }
 
   return rv;
 }
 
-bool
-HTMLPictureElement::IsPictureEnabled()
-{
-  return HTMLImageElement::IsSrcsetEnabled() &&
-         Preferences::GetBool(kPrefPictureEnabled, false);
-}
-
 JSObject*
 HTMLPictureElement::WrapNode(JSContext* aCx, JS::Handle<JSObject*> aGivenProto)
 {
   return HTMLPictureElementBinding::Wrap(aCx, this, aGivenProto);
 }
 
 } // namespace dom
 } // namespace mozilla

--- a/dom/html/HTMLPictureElement.h
+++ b/dom/html/HTMLPictureElement.h
@@ -6,18 +6,16 @@
 
 #ifndef mozilla_dom_HTMLPictureElement_h
 #define mozilla_dom_HTMLPictureElement_h
 
 #include "mozilla/Attributes.h"
 #include "nsIDOMHTMLPictureElement.h"
 #include "nsGenericHTMLElement.h"
 
-#include "mozilla/dom/HTMLUnknownElement.h"
-
 namespace mozilla {
 namespace dom {
 
 class HTMLPictureElement final : public nsGenericHTMLElement,
                                  public nsIDOMHTMLPictureElement
 {
 public:
   explicit HTMLPictureElement(already_AddRefed<mozilla::dom::NodeInfo>& aNodeInfo);
@@ -27,18 +25,16 @@ public:
 
   // nsIDOMHTMLPictureElement
   NS_DECL_NSIDOMHTMLPICTUREELEMENT
 
   virtual nsresult Clone(mozilla::dom::NodeInfo* aNodeInfo, nsINode** aResult) const override;
   virtual void RemoveChildAt(uint32_t aIndex, bool aNotify) override;
   virtual nsresult InsertChildAt(nsIContent* aKid, uint32_t aIndex, bool aNotify) override;
 
-  static bool IsPictureEnabled();
-
 protected:
   virtual ~HTMLPictureElement();
 
   virtual JSObject* WrapNode(JSContext* aCx, JS::Handle<JSObject*> aGivenProto) override;
 };
 
 } // namespace dom
 } // namespace mozilla

--- a/dom/html/crashtests/crashtests.list
+++ b/dom/html/crashtests/crashtests.list
@@ -66,14 +66,14 @@ load 837033.html
 load 838256-1.html
 load 862084.html
 load 865147.html
 load 877910.html
 load 903106.html
 load 916322-1.html
 load 916322-2.html
 load 1032654.html
-pref(dom.image.srcset.enabled,true) load 1141260.html
+load 1141260.html
 load 1228876.html
 load 1230110.html
 load 1237633.html
 load 1281972-1.html
 load 1282894.html
\ No newline at end of file

--- a/dom/html/reftests/reftest-stylo.list
+++ b/dom/html/reftests/reftest-stylo.list
@@ -43,18 +43,18 @@ random == responsive-image-load-shortcir
 # (Fuzzy necessary due to pixel-wise comparison of different JPEGs.
 # The vast majority of the fuzziness comes from Linux and WinXP.)
 skip == bug917595-iframe-1.html bug917595-iframe-1.html
 skip == bug917595-exif-rotated.jpg bug917595-exif-rotated.jpg
 # bug 1060869
 # Bug 1150490 disabling on Mulet as on B2G
 
 # Test support for SVG-as-image in <picture> elements.
-pref(dom.image.picture.enabled,true) pref(dom.image.srcset.enabled,true) == bug1106522-1.html bug1106522-1.html
-pref(dom.image.picture.enabled,true) pref(dom.image.srcset.enabled,true) == bug1106522-2.html bug1106522-2.html
+== bug1106522-1.html bug1106522-1.html
+== bug1106522-2.html bug1106522-2.html
 
 == href-attr-change-restyles.html href-attr-change-restyles.html
 == figure.html figure.html
 == pre-1.html pre-1.html
 == table-border-1.html table-border-1.html
 == table-border-2.html table-border-2.html
 == table-border-2.html table-border-2.html
 

--- a/dom/html/reftests/reftest.list
+++ b/dom/html/reftests/reftest.list
@@ -39,18 +39,18 @@ skip-if(Android||B2G) == 649134-2.html 6
 # Test that image documents taken into account CSS properties like
 # image-orientation when determining the size of the image.
 # (Fuzzy necessary due to pixel-wise comparison of different JPEGs.
 # The vast majority of the fuzziness comes from Linux and WinXP.)
 fuzzy(1,149) == bug917595-iframe-1.html    bug917595-1-ref.html
 skip-if(B2G||Mulet) fuzzy-if((!B2G&&!Mulet),3,640) == bug917595-exif-rotated.jpg bug917595-pixel-rotated.jpg # bug 1060869 # Bug 1150490 disabling on Mulet as on B2G
 
 # Test support for SVG-as-image in <picture> elements.
-pref(dom.image.picture.enabled,true) pref(dom.image.srcset.enabled,true) == bug1106522-1.html bug1106522-ref.html
-pref(dom.image.picture.enabled,true) pref(dom.image.srcset.enabled,true) == bug1106522-2.html bug1106522-ref.html
+== bug1106522-1.html bug1106522-ref.html
+== bug1106522-2.html bug1106522-ref.html
 
 == href-attr-change-restyles.html href-attr-change-restyles-ref.html
 == figure.html figure-ref.html
 == pre-1.html pre-1-ref.html
 == table-border-1.html table-border-1-ref.html
 == table-border-2.html table-border-2-ref.html
 != table-border-2.html table-border-2-notref.html
 

--- a/dom/security/test/mixedcontentblocker/test_main.html
+++ b/dom/security/test/mixedcontentblocker/test_main.html
@@ -161,26 +161,23 @@ https://bugzilla.mozilla.org/show_bug.cg
     checkTestsCompleted();
   }
 
   function startTest() {
     // Set prefs to use mixed-content before HSTS
     SpecialPowers.pushPrefEnv({'set': [["security.mixed_content.use_hsts", false],
                                        ["security.mixed_content.send_hsts_priming", false]]});
     //Set the first set of mixed content settings and increment the counter.
-    //Enable <picture> and <img srcset> for the test.
-    changePrefs([[ "dom.image.srcset.enabled", true ], [ "dom.image.picture.enabled", true ]],
-      function() {
-        //listen for a messages from the mixed content test harness
-        window.addEventListener("message", receiveMessage, false);
+    changePrefs([], function() {
+      //listen for a messages from the mixed content test harness
+      window.addEventListener("message", receiveMessage, false);
 
-        //Kick off test
-        reloadFrame();
-      }
-    );
+      //Kick off test
+      reloadFrame();
+    });
   }
 
   SimpleTest.waitForExplicitFinish();
 
   </script>
 </head>
 
 <body onload='startTest()'>

--- a/dom/tests/mochitest/general/mochitest.ini
+++ b/dom/tests/mochitest/general/mochitest.ini
@@ -95,24 +95,22 @@ skip-if = ((buildapp == 'mulet' || build
 support-files = test_offsets.js
 [test_outerHTML.html]
 [test_outerHTML.xhtml]
 skip-if = buildapp == 'mulet'
 [test_paste_selection.html]
 skip-if = buildapp == 'mulet'
 [test_performance_timeline.html]
 [test_picture_mutations.html]
-[test_picture_pref.html]
 skip-if = buildapp == 'b2g' || buildapp == 'mulet'
 [test_resource_timing.html]
 skip-if = buildapp == 'b2g' || buildapp == 'mulet'
 [test_resource_timing_cross_origin.html]
 skip-if = buildapp == 'b2g' || buildapp == 'mulet'
 [test_performance_now.html]
-[test_srcset_pref.html]
 [test_showModalDialog.html]
 skip-if = e10s || buildapp == 'mulet' || buildapp == 'b2g' || toolkit == 'android' #Don't run modal tests on Android # b2g(showmodaldialog) b2g-debug(showmodaldialog) b2g-desktop(showmodaldialog)
 [test_showModalDialog_e10s.html]
 run-if = e10s
 [test_stylesheetPI.html]
 [test_vibrator.html]
 [test_windowProperties.html]
 skip-if = (buildapp == 'b2g' && toolkit != 'gonk') #Bug 931116, b2g desktop specific, initial triage

--- a/dom/tests/mochitest/general/test_img_mutations.html
+++ b/dom/tests/mochitest/general/test_img_mutations.html
@@ -213,18 +213,17 @@
         // causing test failures.
         img.removeEventListener("load", onImgLoad);
         img.removeEventListener("error", onImgError);
         SimpleTest.finish();
       }
     }
 
     addEventListener("load", function() {
-      SpecialPowers.pushPrefEnv({'set': [ ["layout.css.devPixelsPerPx", "1.0"],
-                                          [ "dom.image.srcset.enabled", true ]] },
+      SpecialPowers.pushPrefEnv({'set': [["layout.css.devPixelsPerPx", "1.0"]] },
                                 function() {
         // Create this after the pref is set, as it is guarding webIDL attributes
         img = document.createElement("img");
         img.addEventListener("load", onImgLoad);
         img.addEventListener("error", onImgError);
         document.body.appendChild(img);
         setTimeout(nextTest, 0);
       });

--- a/dom/tests/mochitest/general/test_picture_mutations.html
+++ b/dom/tests/mochitest/general/test_picture_mutations.html
@@ -288,19 +288,17 @@
         // Ignore it all.
         img.removeEventListener("load", onImgLoad);
         img.removeEventListener("error", onImgError);
         SimpleTest.finish();
       }
     }
 
     addEventListener("load", function() {
-      SpecialPowers.pushPrefEnv({'set': [ ["layout.css.devPixelsPerPx", "1.0" ],
-                                          [ "dom.image.srcset.enabled",  true ],
-                                          [ "dom.image.picture.enabled", true ]] },
+      SpecialPowers.pushPrefEnv({'set': [["layout.css.devPixelsPerPx", "1.0" ]] },
                                 function() {
         // Create these after the pref is set, as it is guarding webIDL attributes
         img = document.createElement("img");
         img.addEventListener("load", onImgLoad);
         img.addEventListener("error", onImgError);
         picture = document.createElement("picture");
         source1 = document.createElement("source");
         source2 = document.createElement("source");

deleted file mode 100644
--- a/dom/tests/mochitest/general/test_picture_pref.html
+++ /dev/null
@@ -1,108 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<!--
-https://bugzilla.mozilla.org/show_bug.cgi?id=870022
--->
-<head>
-  <title>Test for dom.image.picture.enabled (Bug 870022)</title>
-  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
-</head>
-<body onload="setupTest()">
-<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=870022">Mozilla Bug 870022</a>
-
-<!-- Tests that the picture pref can still be disabled, accounting
-     for dom.images.srcset.enabled being flipped on in the mean time. -->
-
-<!-- these should all load red.png (naturalWidth 1) not big.png (natural
-     width 3000) regardless of dom.images.srcset.enabled being on or off -->
-
-<div id="testContainer">
-<picture>
-  <source srcset="http://example.com/tests/image/test/mochitest/big.png">
-  <img id="img1" src="http://example.com/tests/image/test/mochitest/red.png">
-</picture>
-
-<picture>
-  <source srcset="http://example.com/tests/image/test/mochitest/big.png 500w"
-          sizes="500w">
-  <img id="img2"
-       src="http://example.com/tests/image/test/mochitest/red.png"
-       srcset="http://example.com/tests/image/test/mochitest/big.png 500w"
-       sizes="50px">
-</picture>
-
-<!-- Should load red.png with srcset on, otherwise nothing -->
-<img id="img-srcset-only"
-     srcset="http://example.com/tests/image/test/mochitest/big.png 500w, http://example.com/tests/image/test/mochitest/red.png 1x"
-     sizes="50px">
-
-<!-- Should not load regardless of srcset pref -->
-<img id="img-never"
-     srcset="http://example.com/tests/image/test/mochitest/big.png 500w"
-     sizes="50px">
-</div>
-
-<script type="application/javascript">
-
-  const srcsetPref  = 'dom.image.srcset.enabled';
-  const picturePref = 'dom.image.picture.enabled';
-
-  SimpleTest.waitForExplicitFinish();
-
-  var srcsetEnabled = SpecialPowers.getBoolPref(srcsetPref);
-  var pictureEnabled = SpecialPowers.getBoolPref(picturePref);
-
-  is(pictureEnabled, true, "picture expected to be enabled by default");
-
-  function setupTest() {
-    SpecialPowers.pushPrefEnv({'set': [[ "dom.image.picture.enabled", false ]] }, function() {
-      var container = document.querySelector("#testContainer");
-      // We want to re-create the elements with the pref disabled to ensure
-      // webIDL attributes are not attached
-      var iframe = document.createElement("iframe");
-      iframe.addEventListener("load", function() {
-        runTest(iframe);
-      });
-      document.body.appendChild(iframe);
-      iframe.src = "data:text/html;base64," + btoa(container.innerHTML);
-    });
-  }
-
-  function runTest(iframe) {
-    var doc = iframe.contentDocument;
-    var win = iframe.contentWindow;
-    var img = doc.querySelector("img");
-    var source = doc.querySelector("source");
-
-    is(img.sizes, undefined, "sizes should not be visible on <img>");
-    is(source.sizes, undefined, "sizes should not be visible on <source>");
-    is(source.srcset, undefined, "srcset should not be visible on <source>");
-
-    var imgSizesDesc = Object.getOwnPropertyDescriptor(win.HTMLImageElement.prototype, "sizes");
-    var sourceSizesDesc = Object.getOwnPropertyDescriptor(win.HTMLSourceElement.prototype, "sizes");
-    var sourceSrcsetDesc = Object.getOwnPropertyDescriptor(win.HTMLSourceElement.prototype, "srcset");
-    is(imgSizesDesc, undefined, "HTMLImageElement should know nothing of sizes");
-    is(sourceSizesDesc, undefined, "HTMLSourceElement should know nothing of sizes");
-    is(sourceSrcsetDesc, undefined, "HTMLSourceElement should know nothing of srcset");
-
-    // Make sure the test images loaded red.png, which is 1x1, not big.png
-    for (var id of [ 'img1', 'img2' ]) {
-      var testImg = doc.getElementById(id);
-      is(testImg.naturalWidth, 1, "Image should have loaded small source");
-    }
-
-    var srcsetOnlyImg = doc.getElementById("img-srcset-only");
-    is(srcsetOnlyImg.naturalWidth, srcsetEnabled ? 1 : 0,
-       "srcset image should only load if srcset is enabled, and never the computed width candidate");
-
-    var neverImg = doc.getElementById("img-never");
-    is(neverImg.naturalWidth, 0, "Image should not have loaded");
-
-    SimpleTest.finish();
-  }
-
-</script>
-
-</body>
-</html>

deleted file mode 100644
--- a/dom/tests/mochitest/general/test_srcset_pref.html
+++ /dev/null
@@ -1,59 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<!--
-https://bugzilla.mozilla.org/show_bug.cgi?id=870021
--->
-<head>
-  <title>Test for dom.image.srcset.enabled (Bug 870021)</title>
-  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
-</head>
-<body onload="setupTest()">
-<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=870021">Mozilla Bug 870021</a>
-
-<div id="imgContainer">
-</div>
-
-<script type="application/javascript">
-
-  const srcsetPref = 'dom.image.srcset.enabled';
-
-  SimpleTest.waitForExplicitFinish();
-
-  is(SpecialPowers.getBoolPref(srcsetPref), true, "srcset should be enabled by default");
-
-  function setupTest() {
-    // Ensure that disabling the pref works as expected
-    SpecialPowers.pushPrefEnv({'set': [[ "dom.image.srcset.enabled", false ]] }, function() {
-      var container = document.querySelector("#imgContainer");
-
-      var img = document.createElement("img");
-      img.setAttribute("src", "http://example.com/tests/image/test/mochitest/blue.png");
-      img.setAttribute("srcset", "http://example.com/tests/image/test/mochitest/big.png");
-      container.insertBefore(img, container.firstChild);
-      img.addEventListener("load", function imgLoad() {
-        img.removeEventListener("load", imgLoad);
-        runTest();
-      });
-    });
-  }
-
-  function runTest() {
-    var img = document.querySelector("img");
-    is(img.currentSrc, undefined, "currentSrc should not be visible");
-    is(img.srcset, undefined, "srcset should not be visible");
-
-    var currentSrcDesc = Object.getOwnPropertyDescriptor(HTMLImageElement.prototype, "currentSrc");
-    var srcsetDesc = Object.getOwnPropertyDescriptor(HTMLImageElement.prototype, "srcset");
-    is(currentSrcDesc, undefined, "HTMLImageElement should know nothing of currentSrc");
-    is(srcsetDesc, undefined, "HTMLImageElement should know nothing of srcset");
-
-    // Make sure the test image loaded the src image, which is 1x1, not the srcset image
-    is(img.naturalWidth, 1, "Image should have loaded small source");
-    SimpleTest.finish();
-  }
-
-</script>
-
-</body>
-</html>

--- a/dom/webidl/HTMLImageElement.webidl
+++ b/dom/webidl/HTMLImageElement.webidl
@@ -17,17 +17,17 @@ interface URI;
 interface nsIStreamListener;
 
 [NamedConstructor=Image(optional unsigned long width, optional unsigned long height)]
 interface HTMLImageElement : HTMLElement {
            [SetterThrows]
            attribute DOMString alt;
            [SetterThrows]
            attribute DOMString src;
-           [SetterThrows, Pref="dom.image.srcset.enabled"]
+           [SetterThrows]
            attribute DOMString srcset;
            [SetterThrows]
            attribute DOMString? crossOrigin;
            [SetterThrows]
            attribute DOMString useMap;
            [SetterThrows, Pref="network.http.enablePerElementReferrer"]
            attribute DOMString referrerPolicy;
            [SetterThrows]
@@ -55,19 +55,18 @@ partial interface HTMLImageElement {
            attribute DOMString longDesc;
 
   [TreatNullAs=EmptyString,SetterThrows] attribute DOMString border;
 };
 
 // [Update me: not in whatwg spec yet]
 // http://picture.responsiveimages.org/#the-img-element
 partial interface HTMLImageElement {
-           [SetterThrows, Pref="dom.image.picture.enabled"]
+           [SetterThrows]
            attribute DOMString sizes;
-           [Pref="dom.image.srcset.enabled"]
   readonly attribute DOMString currentSrc;
 };
 
 // Mozilla extensions.
 partial interface HTMLImageElement {
            attribute DOMString lowsrc;
 
   // These attributes are offsets from the closest view (to mimic

--- a/dom/webidl/HTMLPictureElement.webidl
+++ b/dom/webidl/HTMLPictureElement.webidl
@@ -1,9 +1,8 @@
 /* -*- 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/.
  */
 
-[Pref="dom.image.picture.enabled"]
 interface HTMLPictureElement : HTMLElement {
 };

--- a/dom/webidl/HTMLSourceElement.webidl
+++ b/dom/webidl/HTMLSourceElement.webidl
@@ -14,15 +14,15 @@
 interface HTMLSourceElement : HTMLElement {
            [SetterThrows]
            attribute DOMString src;
            [SetterThrows]
            attribute DOMString type;
 };
 
 partial interface HTMLSourceElement {
-           [SetterThrows, Pref="dom.image.picture.enabled"]
+           [SetterThrows]
            attribute DOMString srcset;
-           [SetterThrows, Pref="dom.image.picture.enabled"]
+           [SetterThrows]
            attribute DOMString sizes;
            [SetterThrows]
            attribute DOMString media;
 };

--- a/dom/workers/test/serviceworkers/test_request_context.js
+++ b/dom/workers/test/serviceworkers/test_request_context.js
@@ -61,16 +61,14 @@ function runTest() {
 
 SimpleTest.waitForExplicitFinish();
 onload = function() {
   SpecialPowers.pushPrefEnv({"set": [
     ["beacon.enabled", true],
     ["browser.send_pings", true],
     ["browser.send_pings.max_per_link", -1],
     ["dom.caches.enabled", true],
-    ["dom.image.picture.enabled", true],
-    ["dom.image.srcset.enabled", true],
     ["dom.requestcontext.enabled", true],
     ["dom.serviceWorkers.exemptFromPerDomainMax", true],
     ["dom.serviceWorkers.enabled", true],
     ["dom.serviceWorkers.testing.enabled", true],
   ]}, runTest);
 };

--- a/layout/reftests/image/reftest-stylo.list
+++ b/layout/reftests/image/reftest-stylo.list
@@ -116,22 +116,22 @@ skip == image-srcset-basic-selection-2x.
 skip == image-srcset-basic-selection-0.5x.html image-srcset-basic-selection-0.5x.html
 skip == image-srcset-basic-selection-0.6x.html image-srcset-basic-selection-0.6x.html
 skip == image-srcset-basic-selection-1.5x.html image-srcset-basic-selection-1.5x.html
 skip == image-srcset-basic-selection-1x.html image-srcset-basic-selection-1x.html
 skip == image-srcset-basic-selection-width-0.5x.html image-srcset-basic-selection-width-0.5x.html
 skip == image-srcset-basic-selection-width-10x.html image-srcset-basic-selection-width-10x.html
 skip == image-srcset-basic-selection-width-2x.html image-srcset-basic-selection-width-2x.html
 skip == image-srcset-basic-selection-width-1x.html image-srcset-basic-selection-width-1x.html
-pref(dom.image.srcset.enabled,true) == image-srcset-default-2x.html image-srcset-default-2x.html
-pref(dom.image.srcset.enabled,true) == image-srcset-default-1x.html image-srcset-default-1x.html
-pref(dom.image.srcset.enabled,true) == image-srcset-default-src-2x.html image-srcset-default-src-2x.html
-pref(dom.image.srcset.enabled,true) == image-srcset-default-src-1x.html image-srcset-default-src-1x.html
-pref(dom.image.srcset.enabled,true) == image-srcset-orientation-2x.html image-srcset-orientation-2x.html
-pref(dom.image.srcset.enabled,true) == image-srcset-orientation-1x.html image-srcset-orientation-1x.html
-pref(dom.image.srcset.enabled,true) == image-srcset-svg-3x.html image-srcset-svg-3x.html
-pref(dom.image.srcset.enabled,true) == image-srcset-svg-2x.html image-srcset-svg-2x.html
-pref(dom.image.srcset.enabled,true) == image-srcset-svg-1x.html image-srcset-svg-1x.html
-pref(dom.image.srcset.enabled,true) == image-srcset-svg-default-2x.html image-srcset-svg-default-2x.html
-pref(dom.image.srcset.enabled,true) == image-srcset-svg-default-1x.html image-srcset-svg-default-1x.html
+== image-srcset-default-2x.html image-srcset-default-2x.html
+== image-srcset-default-1x.html image-srcset-default-1x.html
+== image-srcset-default-src-2x.html image-srcset-default-src-2x.html
+== image-srcset-default-src-1x.html image-srcset-default-src-1x.html
+== image-srcset-orientation-2x.html image-srcset-orientation-2x.html
+== image-srcset-orientation-1x.html image-srcset-orientation-1x.html
+== image-srcset-svg-3x.html image-srcset-svg-3x.html
+== image-srcset-svg-2x.html image-srcset-svg-2x.html
+== image-srcset-svg-1x.html image-srcset-svg-1x.html
+== image-srcset-svg-default-2x.html image-srcset-svg-default-2x.html
+== image-srcset-svg-default-1x.html image-srcset-svg-default-1x.html
 
 == image-resize-percent-height.html image-resize-percent-height.html
 == image-resize-percent-width.html image-resize-percent-width.html

--- a/layout/reftests/image/reftest.list
+++ b/layout/reftests/image/reftest.list
@@ -97,32 +97,32 @@ fuzzy(1,1) == image-orientation-backgrou
 != image-orientation-generated-content-ref.html?180  image-orientation-generated-content-ref.html?270
 != image-orientation-generated-content-ref.html?0    image-orientation-generated-content-ref.html?0&flip
 != image-orientation-generated-content-ref.html?90   image-orientation-generated-content-ref.html?90&flip
 != image-orientation-generated-content-ref.html?180  image-orientation-generated-content-ref.html?180&flip
 != image-orientation-generated-content-ref.html?270  image-orientation-generated-content-ref.html?270&flip
 == image-orientation-dynamic.html image-orientation-dynamic-ref.html
 
 # <img srcset> tests
-pref(dom.image.srcset.enabled,true) == image-srcset-basic-selection-0.1x.html image-srcset-basic-selection-0.1x-ref.html
-pref(dom.image.srcset.enabled,true) == image-srcset-basic-selection-2x.html image-srcset-basic-selection-2x-ref.html
-pref(dom.image.srcset.enabled,true) == image-srcset-basic-selection-0.5x.html image-srcset-basic-selection-0.5x-ref.html
-pref(dom.image.srcset.enabled,true) == image-srcset-basic-selection-0.6x.html image-srcset-basic-selection-0.6x-ref.html
-pref(dom.image.srcset.enabled,true) == image-srcset-basic-selection-1.5x.html image-srcset-basic-selection-1.5x-ref.html
-pref(dom.image.srcset.enabled,true) == image-srcset-basic-selection-1x.html image-srcset-basic-selection-1x-ref.html
-pref(dom.image.srcset.enabled,true) == image-srcset-basic-selection-width-0.5x.html image-srcset-basic-selection-width-0.5x-ref.html
-pref(dom.image.srcset.enabled,true) == image-srcset-basic-selection-width-10x.html image-srcset-basic-selection-width-10x-ref.html
-pref(dom.image.srcset.enabled,true) == image-srcset-basic-selection-width-2x.html image-srcset-basic-selection-width-2x-ref.html
-pref(dom.image.srcset.enabled,true) == image-srcset-basic-selection-width-1x.html image-srcset-basic-selection-width-1x-ref.html
-pref(dom.image.srcset.enabled,true) == image-srcset-default-2x.html image-srcset-default-2x-ref.html
-pref(dom.image.srcset.enabled,true) == image-srcset-default-1x.html image-srcset-default-1x-ref.html
-pref(dom.image.srcset.enabled,true) == image-srcset-default-src-2x.html image-srcset-default-src-2x-ref.html
-pref(dom.image.srcset.enabled,true) == image-srcset-default-src-1x.html image-srcset-default-src-1x-ref.html
-pref(dom.image.srcset.enabled,true) == image-srcset-orientation-2x.html image-srcset-orientation-2x-ref.html
-pref(dom.image.srcset.enabled,true) == image-srcset-orientation-1x.html image-srcset-orientation-1x-ref.html
-pref(dom.image.srcset.enabled,true) == image-srcset-svg-3x.html image-srcset-svg-3x-ref.html
-pref(dom.image.srcset.enabled,true) == image-srcset-svg-2x.html image-srcset-svg-2x-ref.html
-pref(dom.image.srcset.enabled,true) == image-srcset-svg-1x.html image-srcset-svg-1x-ref.html
-pref(dom.image.srcset.enabled,true) == image-srcset-svg-default-2x.html image-srcset-svg-default-2x-ref.html
-pref(dom.image.srcset.enabled,true) == image-srcset-svg-default-1x.html image-srcset-svg-default-1x-ref.html
+== image-srcset-basic-selection-0.1x.html image-srcset-basic-selection-0.1x-ref.html
+== image-srcset-basic-selection-2x.html image-srcset-basic-selection-2x-ref.html
+== image-srcset-basic-selection-0.5x.html image-srcset-basic-selection-0.5x-ref.html
+== image-srcset-basic-selection-0.6x.html image-srcset-basic-selection-0.6x-ref.html
+== image-srcset-basic-selection-1.5x.html image-srcset-basic-selection-1.5x-ref.html
+== image-srcset-basic-selection-1x.html image-srcset-basic-selection-1x-ref.html
+== image-srcset-basic-selection-width-0.5x.html image-srcset-basic-selection-width-0.5x-ref.html
+== image-srcset-basic-selection-width-10x.html image-srcset-basic-selection-width-10x-ref.html
+== image-srcset-basic-selection-width-2x.html image-srcset-basic-selection-width-2x-ref.html
+== image-srcset-basic-selection-width-1x.html image-srcset-basic-selection-width-1x-ref.html
+== image-srcset-default-2x.html image-srcset-default-2x-ref.html
+== image-srcset-default-1x.html image-srcset-default-1x-ref.html
+== image-srcset-default-src-2x.html image-srcset-default-src-2x-ref.html
+== image-srcset-default-src-1x.html image-srcset-default-src-1x-ref.html
+== image-srcset-orientation-2x.html image-srcset-orientation-2x-ref.html
+== image-srcset-orientation-1x.html image-srcset-orientation-1x-ref.html
+== image-srcset-svg-3x.html image-srcset-svg-3x-ref.html
+== image-srcset-svg-2x.html image-srcset-svg-2x-ref.html
+== image-srcset-svg-1x.html image-srcset-svg-1x-ref.html
+== image-srcset-svg-default-2x.html image-srcset-svg-default-2x-ref.html
+== image-srcset-svg-default-1x.html image-srcset-svg-default-1x-ref.html
 
 == image-resize-percent-height.html image-resize-ref.html
 == image-resize-percent-width.html image-resize-ref.html

--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -4723,22 +4723,16 @@ pref("layout.animated-image-layers.enabl
 
 pref("dom.vibrator.enabled", true);
 pref("dom.vibrator.max_vibrate_ms", 10000);
 pref("dom.vibrator.max_vibrate_list_len", 128);
 
 // Battery API
 pref("dom.battery.enabled", true);
 
-// Image srcset
-pref("dom.image.srcset.enabled", true);
-
-// <picture> element and sizes
-pref("dom.image.picture.enabled", true);
-
 // WebSMS
 pref("dom.sms.enabled", false);
 // Enable Latin characters replacement with corresponding ones in GSM SMS
 // 7-bit default alphabet.
 pref("dom.sms.strict7BitEncoding", false);
 pref("dom.sms.requestStatusReport", true);
 // Numeric default service id for SMS API calls with |serviceId| parameter
 // omitted.