Move handling of DraggableRegionsChanged notification from "view" to "frame".

extensions/browser/app_window/app_window_contents.cc

Index: extensions/browser/app_window/app_window_contents.cc
diff --git a/extensions/browser/app_window/app_window_contents.cc b/extensions/browser/app_window/app_window_contents.cc
index 2478ddeba03723437966037bc5b854f3b7e9aeee..875d2cceb215847428927b4b90990a65d252272a 100644
--- a/extensions/browser/app_window/app_window_contents.cc
+++ b/extensions/browser/app_window/app_window_contents.cc
@@ -97,9 +97,11 @@ WindowController* AppWindowContentsImpl::GetWindowController() const {
   return nullptr;
 }
 
-bool AppWindowContentsImpl::OnMessageReceived(const IPC::Message& message) {
+bool AppWindowContentsImpl::OnMessageReceived(
+    const IPC::Message& message,
+    content::RenderFrameHost* sender) {
   bool handled = true;
-  IPC_BEGIN_MESSAGE_MAP(AppWindowContentsImpl, message)
+  IPC_BEGIN_MESSAGE_MAP_WITH_PARAM(AppWindowContentsImpl, message, sender)
     IPC_MESSAGE_HANDLER(ExtensionHostMsg_UpdateDraggableRegions,
                         UpdateDraggableRegions)
     IPC_MESSAGE_UNHANDLED(handled = false)
@@ -114,8 +116,10 @@ void AppWindowContentsImpl::ReadyToCommitNavigation(
 }
 
 void AppWindowContentsImpl::UpdateDraggableRegions(
+    content::RenderFrameHost* sender,
     const std::vector<DraggableRegion>& regions) {
-  host_->UpdateDraggableRegions(regions);
+  if (!sender->GetParent())  // Only process events from the main frame.
+    host_->UpdateDraggableRegions(regions);
 }
 
 void AppWindowContentsImpl::SuspendRenderFrameHost(