Make RenderFrameHostImpl::GetRenderWidgetHost() always return an object

content/browser/frame_host/render_frame_host_impl.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_IMPL_H_
 #define CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 234 matching lines @@
   // FrameTreeNode. The proper way to check whether a frame is loading is to
   // call FrameTreeNode::IsLoading.
   bool is_loading() const { return is_loading_; }
 
   // Sets this RenderFrameHost loading state. This is only used in the case of
   // transfer navigations, where no DidStart/DidStopLoading notifications
   // should be sent during the transfer.
   // TODO(clamy): Remove this once PlzNavigate ships.
   void set_is_loading(bool is_loading) { is_loading_ = is_loading; }
 
-  // This returns the RenderFrameHost's owned RenderWidgetHost if it has one,
-  // or else it returns nullptr.
-  // If the RenderFrameHost is the page's main frame, this returns instead a
-  // pointer to the RenderViewHost (which inherits RenderWidgetHost).
+  // Returns the RenderWidgetHostImpl attached to this frame or the nearest

[Charlie Reis, 2016/05/27 22:50:28]

nit: owned by this frame or its nearest

(Is that accurate enough?  I realize the root widget is technically still owned
by the RVH, but it kind of seems like every frame is attached to a widget.)

[kenrb, 2016/05/30 19:39:54]

I think it's accurate enough. Even though technically the root frame doesn't
(yet) own its widget, it still has its render_widget_host_ pointer set as if it
does.

+  // ancestor frame, which could potentially be the root. For most input
+  // and rendering related purposes, GetView() should be preferred and
+  // RenderWidgetHostViewBase methods used. Unlike GetView(),
+  // GetRenderWidgetHost() will not return a nullptr.

[Charlie Reis, 2016/05/27 22:50:28]

nit: nullptr after a renderer crash.

(Helpful to give more context about when GetView is null.)

[kenrb, 2016/05/30 19:39:54]

Done.

+  //
+  // This method crashes if this RenderFrameHostImpl is not attached to the
+  // frame tree.

[Charlie Reis, 2016/05/27 22:50:28]

nit: if this RenderFrameHost has no RenderWidgetHost in any of its ancestors,
which could happen if it has been detached from the frame tree.

[kenrb, 2016/05/30 19:39:54]

Done.

   RenderWidgetHostImpl* GetRenderWidgetHost();
 
+  // Returns true if this is a top-level frame, or if this frame's RenderFrame
+  // is in a different process from its parent frame. Local roots are
+  // distinguished by owning a RenderWidgetHost, which manages input events
+  // and painting for this frame and its contiguous local subtree in the
+  // renderer process.
+  bool IsLocalRoot();

[Charlie Reis, 2016/05/27 22:50:28]

nit: Let's move this above GetRenderWidgetHost(), since it's a useful concept
for understanding the comment on GetRenderWidgetHost().

This can also be is_local_root() and inlined into the .h file, since it's
trivial and not virtual.

[kenrb, 2016/05/30 19:39:54]

Done.

+
   GlobalFrameRoutingId GetGlobalFrameRoutingId();
 
   // This function is called when this is a swapped out RenderFrameHost that
   // lives in the same process as the parent frame. The
   // |cross_process_frame_connector| allows the non-swapped-out
   // RenderFrameHost for a frame to communicate with the parent process
   // so that it may composite drawing data.
   //
   // Ownership is not transfered.
   void set_cross_process_frame_connector(
@@ skipping 708 matching lines @@
 
   // NOTE: This must be the last member.
   base::WeakPtrFactory<RenderFrameHostImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderFrameHostImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_IMPL_H_