Bug 1075490 - Implement "forcemessagemanager" attribute to allow forcing messageManagers. r=smaug

dom/base/nsFrameLoader.cpp

@@ -2421,7 +2421,13 @@ nsFrameLoader::EnsureMessageManager()
     return rv;
   }
 
-  if (!mIsTopLevelContent && !OwnerIsBrowserOrAppFrame() && !mRemoteFrame) {
+  if (!mIsTopLevelContent &&
+      !OwnerIsBrowserOrAppFrame() &&
+      !mRemoteFrame &&
+      !(mOwnerContent->IsXUL() &&
+        mOwnerContent->AttrValueIs(kNameSpaceID_None,
+                                   nsGkAtoms::forcemessagemanager,
+                                   nsGkAtoms::_true, eCaseMatters))) {
     return NS_OK;
   }
 

dom/base/nsGkAtomList.h

@@ -2117,6 +2117,7 @@ GK_ATOM(DisplayPort, "_displayport")
 GK_ATOM(DisplayPortMargins, "_displayportmargins")
 GK_ATOM(DisplayPortBase, "_displayportbase")
 GK_ATOM(AsyncScrollLayerCreationFailed, "_asyncscrolllayercreationfailed")
+GK_ATOM(forcemessagemanager, "forcemessagemanager")
 
 // Names for system metrics
 GK_ATOM(color_picker_available, "color-picker-available")