--- a/content/base/src/nsDOMBlobBuilder.cpp
+++ b/content/base/src/nsDOMBlobBuilder.cpp
@@ -186,25 +186,25 @@ nsDOMMultipartFile::InitBlob(JSContext* 
 {
   bool nativeEOL = false;
   if (aArgc > 1) {
     if (NS_IsMainThread()) {
       BlobPropertyBag d;
       if (!d.Init(aCx, nullptr, aArgv[1])) {
         return NS_ERROR_TYPE_ERR;
       }
-      mContentType = d.type;
-      nativeEOL = d.endings == EndingTypesValues::Native;
+      mContentType = d.mType;
+      nativeEOL = d.mEndings == EndingTypesValues::Native;
     } else {
       BlobPropertyBagWorkers d;
       if (!d.Init(aCx, nullptr, aArgv[1])) {
         return NS_ERROR_TYPE_ERR;
       }
-      mContentType = d.type;
-      nativeEOL = d.endings == EndingTypesValues::Native;
+      mContentType = d.mType;
+      nativeEOL = d.mEndings == EndingTypesValues::Native;
     }
   }
 
   if (aArgc > 0) {
     if (!aArgv[0].isObject()) {
       return NS_ERROR_TYPE_ERR; // We're not interested
     }
 
@@ -281,19 +281,19 @@ nsDOMMultipartFile::InitFile(JSContext* 
   NS_ENSURE_TRUE(aArgc > 0, NS_ERROR_UNEXPECTED);
 
   bool nativeEOL = false;
   if (aArgc > 1) {
     FilePropertyBag d;
     if (!d.Init(aCx, nullptr, aArgv[1])) {
       return NS_ERROR_TYPE_ERR;
     }
-    mName = d.name;
-    mContentType = d.type;
-    nativeEOL = d.endings == EndingTypesValues::Native;
+    mName = d.mName;
+    mContentType = d.mType;
+    nativeEOL = d.mEndings == EndingTypesValues::Native;
   }
 
   // We expect to get a path to represent as a File object,
   // an nsIFile, or an nsIDOMFile.
   nsCOMPtr<nsIFile> file;
   nsCOMPtr<nsIDOMFile> domFile;
   if (!aArgv[0].isString()) {
     // Lets see if it's an nsIFile

--- a/content/base/src/nsXMLHttpRequest.h
+++ b/content/base/src/nsXMLHttpRequest.h
@@ -154,17 +154,17 @@ public:
     nsCOMPtr<nsIScriptObjectPrincipal> principal = do_QueryInterface(aGlobal);
     if (!window || ! principal) {
       aRv.Throw(NS_ERROR_FAILURE);
       return NULL;
     }
 
     nsRefPtr<nsXMLHttpRequest> req = new nsXMLHttpRequest();
     req->Construct(principal->GetPrincipal(), window);
-    req->InitParameters(aParams.mozAnon, aParams.mozSystem);
+    req->InitParameters(aParams.mMozAnon, aParams.mMozSystem);
     return req.forget();
   }
 
   static already_AddRefed<nsXMLHttpRequest>
   Constructor(JSContext* aCx,
               nsISupports* aGlobal,
               const nsAString& ignored,
               ErrorResult& aRv)

--- a/content/canvas/src/WebGLContext.cpp
+++ b/content/canvas/src/WebGLContext.cpp
@@ -891,22 +891,22 @@ WebGLContext::GetContextAttributes(Nulla
 {
     retval.SetNull();
     if (!IsContextStable())
         return;
 
     dom::WebGLContextAttributes& result = retval.SetValue();
 
     gl::ContextFormat cf = gl->ActualFormat();
-    result.alpha = cf.alpha > 0;
-    result.depth = cf.depth > 0;
-    result.stencil = cf.stencil > 0;
-    result.antialias = cf.samples > 1;
-    result.premultipliedAlpha = mOptions.premultipliedAlpha;
-    result.preserveDrawingBuffer = mOptions.preserveDrawingBuffer;
+    result.mAlpha = cf.alpha > 0;
+    result.mDepth = cf.depth > 0;
+    result.mStencil = cf.stencil > 0;
+    result.mAntialias = cf.samples > 1;
+    result.mPremultipliedAlpha = mOptions.premultipliedAlpha;
+    result.mPreserveDrawingBuffer = mOptions.preserveDrawingBuffer;
 }
 
 bool
 WebGLContext::IsExtensionEnabled(WebGLExtensionID ext) const {
     return mExtensions.SafeElementAt(ext);
 }
 
 /* [noscript] DOMString mozGetUnderlyingParamString(in WebGLenum pname); */

--- a/dom/bindings/Codegen.py
+++ b/dom/bindings/Codegen.py
@@ -6395,17 +6395,18 @@ class CGDictionary(CGThing):
         d = self.dictionary
         if d.parent:
             inheritance = ": public %s " % self.makeClassName(d.parent)
         elif not self.workers:
             inheritance = ": public MainThreadDictionaryBase "
         else:
             inheritance = ""
         memberDecls = ["  %s %s;" %
-                       (self.getMemberType(m), m[0].identifier.name)
+                       (self.getMemberType(m),
+                        self.makeMemberName(m[0].identifier.name))
                        for m in self.memberInfo]
 
         return (string.Template(
                 "struct ${selfName} ${inheritance}{\n"
                 "  ${selfName}() {}\n"
                 "  bool Init(JSContext* cx, JSObject* scopeObj, const JS::Value& val);\n"
                 "  bool ToObject(JSContext* cx, JSObject* parentObject, JS::Value *vp);\n"
                 "\n" +
@@ -6540,38 +6541,35 @@ class CGDictionary(CGThing):
     @staticmethod
     def makeDictionaryName(dictionary, workers):
         suffix = "Workers" if workers else ""
         return dictionary.identifier.name + suffix
 
     def makeClassName(self, dictionary):
         return self.makeDictionaryName(dictionary, self.workers)
 
+    @staticmethod
+    def makeMemberName(name):
+        return "m" + name[0].upper() + name[1:]
+
     def getMemberType(self, memberInfo):
         (member, (templateBody, declType,
                   holderType, dealWithOptional)) = memberInfo
         # We can't handle having a holderType here
         assert holderType is None
         if dealWithOptional:
             declType = CGWrapper(declType, pre="Optional< ", post=" >")
         return declType.define()
 
     def getMemberConversion(self, memberInfo):
         (member, (templateBody, declType,
                   holderType, dealWithOptional)) = memberInfo
         replacements = { "val": "temp",
                          "valPtr": "&temp",
-                         # Use this->%s to refer to members, because we don't
-                         # control the member names and want to make sure we're
-                         # talking about the member, not some local that
-                         # shadows the member.  Another option would be to move
-                         # the guts of init to a static method which is passed
-                         # an explicit reference to our dictionary object, so
-                         # we couldn't screw this up even if we wanted to....
-                         "declName": ("(this->%s)" % member.identifier.name),
+                         "declName": self.makeMemberName(member.identifier.name),
                          # We need a holder name for external interfaces, but
                          # it's scoped down to the conversion so we can just use
                          # anything we want.
                          "holderName": "holder",
                          "obj": "scopeObj" }
         # We can't handle having a holderType here
         assert holderType is None
         if dealWithOptional:
@@ -6589,17 +6587,17 @@ class CGDictionary(CGThing):
         else:
             propId = self.makeIdName(member.identifier.name);
             propCheck = ("JS_HasPropertyById(cx, &val.toObject(), %s, &found)" %
                          propId)
             propGet = ("JS_GetPropertyById(cx, &val.toObject(), %s, &temp)" %
                        propId)
 
         conversionReplacements = {
-            "prop": "(this->%s)" % member.identifier.name,
+            "prop": self.makeMemberName(member.identifier.name),
             "convert": string.Template(templateBody).substitute(replacements),
             "propCheck": propCheck,
             "propGet": propGet
             }
         conversion = ("if (isNull) {\n"
                       "  found = false;\n"
                       "} else if (!${propCheck}) {\n"
                       "  return false;\n"
@@ -6626,24 +6624,17 @@ class CGDictionary(CGThing):
         
         return CGGeneric(
             string.Template(conversion).substitute(conversionReplacements)
             )
 
     def getMemberDefinition(self, memberInfo):
         member = memberInfo[0]
         declType = memberInfo[1][1]
-        # Use this->%s to refer to members, because we don't control
-        # the member names and want to make sure we're talking about
-        # the member, not some local that shadows the member.  Another
-        # option would be to move the guts of init to a static method
-        # which is passed an explicit reference to our dictionary
-        # object, so we couldn't screw this up even if we wanted
-        # to....
-        memberLoc = "(this->%s)" % member.identifier.name
+        memberLoc = self.makeMemberName(member.identifier.name)
         if member.defaultValue:
             memberData = memberLoc
         else:
             # The data is inside the Optional<>
             memberData = "%s.Value()" % memberLoc
 
         if self.workers:
             propDef = (

--- a/dom/bindings/test/TestCodeGen.webidl
+++ b/dom/bindings/test/TestCodeGen.webidl
@@ -505,16 +505,17 @@ dictionary Dict : ParentDict {
   long a;
   long b = 8;
   long z = 9;
   DOMString str;
   DOMString empty = "";
   TestEnum otherEnum = "b";
   DOMString otherStr = "def";
   DOMString? yetAnotherStr = null;
+  DOMString template;
 };
 
 dictionary ParentDict : GrandparentDict {
   long c = 5;
   TestInterface someInterface;
   TestExternalInterface someExternalInterface;
 };
 

--- a/dom/encoding/TextDecoder.cpp
+++ b/dom/encoding/TextDecoder.cpp
@@ -26,17 +26,17 @@ TextDecoder::Init(const nsAString& aEnco
   if (!EncodingUtils::FindEncodingForLabel(label, mEncoding)) {
     aRv.ThrowTypeError(MSG_ENCODING_NOT_SUPPORTED, &label);
     return;
   }
 
   // If the constructor is called with an options argument,
   // and the fatal property of the dictionary is set,
   // set the internal fatal flag of the decoder object.
-  mFatal = aFatal.fatal;
+  mFatal = aFatal.mFatal;
 
   // Create a decoder object for mEncoding.
   nsCOMPtr<nsICharsetConverterManager> ccm =
     do_GetService(NS_CHARSETCONVERTERMANAGER_CONTRACTID);
   if (!ccm) {
     aRv.Throw(NS_ERROR_UNEXPECTED);
     return;
   }
@@ -89,17 +89,17 @@ TextDecoder::Decode(const ArrayBufferVie
 
   rv = mDecoder->Convert(data, &length, buf, &outLen);
   MOZ_ASSERT(mFatal || rv != NS_ERROR_ILLEGAL_INPUT);
   buf[outLen] = 0;
   aOutDecodedString.Append(buf, outLen);
 
   // If the internal streaming flag of the decoder object is not set,
   // then reset the encoding algorithm state to the default values
-  if (!aOptions.stream) {
+  if (!aOptions.mStream) {
     mDecoder->Reset();
     if (rv == NS_OK_UDEC_MOREINPUT) {
       if (mFatal) {
         aRv.Throw(NS_ERROR_DOM_ENCODING_DECODE_ERR);
       } else {
         // Need to emit a decode error manually
         // to simulate the EOF handling of the Encoding spec.
         aOutDecodedString.Append(kReplacementChar);

--- a/dom/encoding/TextEncoder.cpp
+++ b/dom/encoding/TextEncoder.cpp
@@ -72,17 +72,17 @@ TextEncoder::Encode(JSContext* aCx,
     return nullptr;
   }
 
   int32_t dstLen = maxLen;
   rv = mEncoder->Convert(data, &srcLen, buf, &dstLen);
 
   // If the internal streaming flag is not set, then reset
   // the encoding algorithm state to the default values for encoding.
-  if (!aOptions.stream) {
+  if (!aOptions.mStream) {
     int32_t finishLen = maxLen - dstLen;
     rv = mEncoder->Finish(buf + dstLen, &finishLen);
     if (NS_SUCCEEDED(rv)) {
       dstLen += finishLen;
     }
   }
 
   JSObject* outView = nullptr;

--- a/dom/network/src/MobileConnection.cpp
+++ b/dom/network/src/MobileConnection.cpp
@@ -162,17 +162,17 @@ MobileConnection::Observe(nsISupports* a
   }
 
   if (!strcmp(aTopic, kUssdReceivedTopic)) {
     mozilla::dom::USSDReceivedEventDict dict;
     bool ok = dict.Init(nsDependentString(aData));
     NS_ENSURE_TRUE(ok, NS_ERROR_FAILURE);
 
     nsRefPtr<USSDReceivedEvent> event =
-      USSDReceivedEvent::Create(dict.message, dict.sessionEnded);
+      USSDReceivedEvent::Create(dict.mMessage, dict.mSessionEnded);
     NS_ASSERTION(event, "This should never fail!");
 
     nsresult rv = event->Dispatch(ToIDOMEventTarget(), USSDRECEIVED_EVENTNAME);
     NS_ENSURE_SUCCESS(rv, rv);
     return NS_OK;
   }
 
   if (!strcmp(aTopic, kDataErrorTopic)) {

--- a/dom/workers/XMLHttpRequest.cpp
+++ b/dom/workers/XMLHttpRequest.cpp
@@ -1498,18 +1498,18 @@ XMLHttpRequest::Constructor(JSContext* a
   nsRefPtr<XMLHttpRequest> xhr = new XMLHttpRequest(aCx, workerPrivate);
 
   if (!Wrap(aCx, aGlobal, xhr)) {
     aRv.Throw(NS_ERROR_FAILURE);
     return NULL;
   }
 
   if (workerPrivate->XHRParamsAllowed()) {
-    xhr->mMozAnon = aParams.mozAnon;
-    xhr->mMozSystem = aParams.mozSystem;
+    xhr->mMozAnon = aParams.mMozAnon;
+    xhr->mMozSystem = aParams.mMozSystem;
   }
 
   xhr->mJSObject = xhr->GetJSObject();
   return xhr;
 }
 
 void
 XMLHttpRequest::ReleaseProxy(ReleaseType aType)