Backout 19ec214f806c (bug 782916), 88b802832f52 (bug 782919), f16429aa2210 (bug 780474) for Android build failures

build/autoconf/compiler-opts.m4

@@ -85,11 +85,7 @@ if test "$CLANG_CXX"; then
     ## returned by C functions. This is possible because we use knowledge about the ABI
     ## to typedef it to a C type with the same layout when the headers are included
     ## from C.
-    ##
-    ## mismatched-tags is disabled (bug 780474) mostly because it's useless.
-    ## Worse, it's not supported by gcc, so it will cause tryserver bustage
-    ## without any easy way for non-Clang users to check for it.
-    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wno-unknown-warning-option -Wno-return-type-c-linkage -Wno-mismatched-tags"
+    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wno-unknown-warning-option -Wno-return-type-c-linkage"
 fi
 
 if test "$GNU_CC"; then

intl/locale/src/mac/nsCollationMacUC.cpp

@@ -56,8 +56,7 @@ nsresult nsCollationMacUC::ConvertLocale(nsILocale* aNSLocale, LocaleRef* aMacLo
 
   nsAutoString localeString;
   nsresult res = aNSLocale->GetCategory(NS_LITERAL_STRING("NSILOCALE_COLLATE"), localeString);
-  NS_ENSURE_TRUE(NS_SUCCEEDED(res) && !localeString.IsEmpty(),
-                 NS_ERROR_FAILURE);
+  NS_ENSURE_TRUE(res == noErr && !localeString.IsEmpty(), NS_ERROR_FAILURE);
   NS_LossyConvertUTF16toASCII tmp(localeString);
   tmp.ReplaceChar('-', '_');
   OSStatus err;

js/src/build/autoconf/compiler-opts.m4

@@ -85,11 +85,7 @@ if test "$CLANG_CXX"; then
     ## returned by C functions. This is possible because we use knowledge about the ABI
     ## to typedef it to a C type with the same layout when the headers are included
     ## from C.
-    ##
-    ## mismatched-tags is disabled (bug 780474) mostly because it's useless.
-    ## Worse, it's not supported by gcc, so it will cause tryserver bustage
-    ## without any easy way for non-Clang users to check for it.
-    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wno-unknown-warning-option -Wno-return-type-c-linkage -Wno-mismatched-tags"
+    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wno-unknown-warning-option -Wno-return-type-c-linkage"
 fi
 
 if test "$GNU_CC"; then

mfbt/Attributes.h

@@ -380,9 +380,7 @@
     * implicit.
     *
     * We have an explicit constructor from int defined, so that casts like
-    * (Enum)7 will still work.  We also have a zero-argument constructor with
-    * no arguments, so declaration without initialization (like "Enum foo;")
-    * will work.
+    * (Enum)7 will still work.
     *
     * Additionally, we'll delete as many operators as possible for the inner
     * enum type, so statements like this will still fail:
@@ -406,7 +404,6 @@
          {
 #  define MOZ_END_ENUM_CLASS(Name) \
          }; \
-         Name() {} \
          Name(Enum aEnum) : mEnum(aEnum) {} \
          explicit Name(int num) : mEnum((Enum)num) {} \
          operator Enum() const { return mEnum; } \