diff --git a/layout/build/nsContentDLF.cpp b/layout/build/nsContentDLF.cpp
index 29fd8647964..7e55e2a6f39 100644
--- a/layout/build/nsContentDLF.cpp
+++ b/layout/build/nsContentDLF.cpp
@@ -86,6 +86,8 @@ static NS_DEFINE_IID(kXULDocumentCID, NS_XULDOCUMENT_CID);
 nsresult
 NS_NewDocumentViewer(nsIDocumentViewer** aResult);
 
+// XXXbz if you change the MIME types here, be sure to update
+// nsIParser.h and DetermineParseMode in nsParser.cpp accordingly.
 static const char* const gHTMLTypes[] = {
   "text/html",
   "text/plain",
diff --git a/parser/htmlparser/public/nsIParser.h b/parser/htmlparser/public/nsIParser.h
index df12c314dad..098bcf230da 100644
--- a/parser/htmlparser/public/nsIParser.h
+++ b/parser/htmlparser/public/nsIParser.h
@@ -383,7 +383,8 @@ const PRUnichar  kLeftSquareBracket  = '[';
 const PRUnichar  kRightSquareBracket = ']';
 const PRUnichar kNullCh           = '\0';
 
-// XXXbz these type defines should really just go away....
+// XXXbz these type defines should really just go away....  Until they
+// do, changes here should be reflected in nsContentDLF.cpp
 #define kHTMLTextContentType  "text/html"
 #define kXMLTextContentType   "text/xml"
 #define kXMLApplicationContentType "application/xml"
@@ -396,7 +397,10 @@ const PRUnichar kNullCh           = '\0';
 #define kViewSourceCommand    "view-source"
 #define kViewFragmentCommand  "view-fragment"
 #define kTextCSSContentType   "text/css"
-#define kApplicationJSContentType   "application/x-javascript"
+#define kApplicationJSContentType "application/javascript"
+#define kApplicationXJSContentType "application/x-javascript"
+#define kTextECMAScriptContentType "text/ecmascript"
+#define kApplicationECMAScriptContentType "application/ecmascript"
 #define kTextJSContentType    "text/javascript"
 #define kSGMLTextContentType   "text/sgml"
 #define kSVGTextContentType   "image/svg+xml"
diff --git a/parser/htmlparser/src/nsExpatDriver.cpp b/parser/htmlparser/src/nsExpatDriver.cpp
index eca64080332..edd3c461908 100644
--- a/parser/htmlparser/src/nsExpatDriver.cpp
+++ b/parser/htmlparser/src/nsExpatDriver.cpp
@@ -1003,10 +1003,13 @@ nsExpatDriver::WillBuildModel(const CParserContext& aParserContext,
                               nsITokenizer* aTokenizer,
                               nsIContentSink* aSink)
 {
-  NS_ENSURE_ARG_POINTER(aSink);
-
   mSink = do_QueryInterface(aSink);
-  NS_ENSURE_TRUE(mSink, NS_ERROR_FAILURE);
+  if (!mSink) {
+    NS_ERROR("nsExpatDriver didn't get an nsIExpatSink");
+    // Make sure future calls to us bail out as needed
+    mInternalState = NS_ERROR_UNEXPECTED;
+    return mInternalState;
+  }
 
   static const XML_Memory_Handling_Suite memsuite =
     {
diff --git a/parser/htmlparser/src/nsParser.cpp b/parser/htmlparser/src/nsParser.cpp
index 6ba3fe84c2e..a0133845d82 100644
--- a/parser/htmlparser/src/nsParser.cpp
+++ b/parser/htmlparser/src/nsParser.cpp
@@ -1151,6 +1151,9 @@ void DetermineParseMode(const nsString& aBuffer,
   } else if (aMimeType.EqualsLiteral(kPlainTextContentType) ||
              aMimeType.EqualsLiteral(kTextCSSContentType) ||
              aMimeType.EqualsLiteral(kApplicationJSContentType) ||
+             aMimeType.EqualsLiteral(kApplicationXJSContentType) ||
+             aMimeType.EqualsLiteral(kTextECMAScriptContentType) ||
+             aMimeType.EqualsLiteral(kApplicationECMAScriptContentType) ||
              aMimeType.EqualsLiteral(kTextJSContentType)) {
     aDocType = ePlainText;
     aParseMode = eDTDMode_quirks;
@@ -2716,7 +2719,9 @@ nsresult nsParser::OnStopRequest(nsIRequest *request, nsISupports* aContext,
   if (mParserFilter)
     mParserFilter->Finish();
 
-  rv = ResumeParse(PR_TRUE, PR_TRUE);
+  if (NS_SUCCEEDED(rv)) {
+    rv = ResumeParse(PR_TRUE, PR_TRUE);
+  }
 
   // If the parser isn't enabled, we don't finish parsing till
   // it is reenabled.