Use a weak pointer when binding GuestViewBase::DidAttach.

The lifetime of GuestViewBase doesn't match the lifetime of GuestViewMessageFilter, so it's possible that the GuestViewBase is already destroyed by the time this callback is called.

BUG=716223

Review-Url: https://codereview.chromium.org/2848723002
Cr-Commit-Position: refs/heads/master@{#468072}

components/guest_view/browser/guest_view_message_filter.cc

@@ -144,7 +144,8 @@ void GuestViewMessageFilter::OnAttachToEmbedderFrame(
 
   guest->WillAttach(
       owner_web_contents, element_instance_id, false,
-      base::Bind(&GuestViewMessageFilter::WillAttachCallback, this, guest));
+      base::Bind(&GuestViewBase::DidAttach,
+                 guest->weak_ptr_factory_.GetWeakPtr(), MSG_ROUTING_NONE));
 
   // Attach this inner WebContents |guest_web_contents| to the outer
   // WebContents |owner_web_contents|. The outer WebContents's
@@ -155,8 +156,4 @@ void GuestViewMessageFilter::OnAttachToEmbedderFrame(
                                                     embedder_frame);
 }
 
-void GuestViewMessageFilter::WillAttachCallback(GuestViewBase* guest) {
-  guest->DidAttach(MSG_ROUTING_NONE);
-}
-
 }  // namespace guest_view

components/guest_view/browser/guest_view_message_filter.h

@@ -23,7 +23,6 @@ class BrowserContext;
 }
 
 namespace guest_view {
-class GuestViewBase;
 class GuestViewManager;
 
 // This class filters out incoming GuestView-specific IPC messages from the
@@ -75,8 +74,6 @@ class GuestViewMessageFilter : public content::BrowserMessageFilter {
   void OnViewCreated(int view_instance_id, const std::string& view_type);
   void OnViewGarbageCollected(int view_instance_id);
 
-  void WillAttachCallback(GuestViewBase* guest);
-
   DISALLOW_COPY_AND_ASSIGN(GuestViewMessageFilter);
 };