Update GetRootRenderWidgetHostView() to explore the tree using RFH.

GetRootRenderWidgetHostView() and GetParentRenderWidget() explore the
FrameTree using FrameTreeNode. Once it is done, it returns the
RenderWidgetHostView associated with the current RenderFrameHost on
that FrameTreeNode.
The issue: there is no 1:1 association between the FrameTreeNode and the
RenderFrameHost. A FrameTreeNode, contains several RenderframeHost:
 * The current one.
 * The pending one, not displayed and used for loading a new document,
   but this one has still not committed.
 * The ones in pending deletion. Those are no more displayed and are
   in progress executing their javascript unload handlers.

Instead of exploring the tree using FrameTreeNode::parent(), explore the
tree using RenderFrameHost::GetParent(). That way, it is guaranteed the
functions will always returns the same object.

Bug: 609963
Change-Id: Ic8972180b94763bd6a831f2754d1e3c661c0bbc4
Reviewed-on: https://chromium-review.googlesource.com/1210942Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Reviewed-by: Lucas Gadani <lfg@chromium.org>
Commit-Queue: Arthur Sonzogni <arthursonzogni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593130}

content/browser/frame_host/cross_process_frame_connector.cc

@@ -34,6 +34,37 @@
 
 namespace content {
 
+namespace {
+
+// If |frame| is an iframe or a GuestView, returns its parent, null otherwise.
+RenderFrameHostImpl* ParentRenderFrameHost(RenderFrameHostImpl* frame) {
+  // Find the parent in the FrameTree (iframe).
+  if (frame->GetParent())
+    return frame->GetParent();
+
+  // Find the parent in the WebContentsTree (GuestView).
+  FrameTreeNode* frame_in_embedder =
+      frame->frame_tree_node()->render_manager()->GetOuterDelegateNode();
+  if (frame_in_embedder)
+    return frame_in_embedder->current_frame_host()->GetParent();
+
+  // No parent found.
+  return nullptr;
+}
+
+// Return the root RenderFrameHost in the outermost WebContents.
+RenderFrameHostImpl* RootRenderFrameHost(RenderFrameHostImpl* frame) {
+  RenderFrameHostImpl* current = frame;
+  while (true) {
+    RenderFrameHostImpl* parent = ParentRenderFrameHost(current);
+    if (!parent)
+      return current;
+    current = parent;
+  };
+}
+
+}  // namespace
+
 CrossProcessFrameConnector::CrossProcessFrameConnector(
     RenderFrameProxyHost* frame_proxy_in_parent_renderer)
     : FrameConnectorDelegate(IsUseZoomForDSFEnabled()),
@@ -393,40 +424,19 @@ CrossProcessFrameConnector::GetRootRenderWidgetHostView() {
   if (!frame_proxy_in_parent_renderer_)
     return nullptr;
 
-  RenderFrameHostImpl* top_host = frame_proxy_in_parent_renderer_->
-      frame_tree_node()->frame_tree()->root()->current_frame_host();
-
-  // This method should return the root RWHV from the top-level WebContents,
-  // in the case of nested WebContents.
-  while (top_host->frame_tree_node()->render_manager()->ForInnerDelegate()) {
-    top_host = top_host->frame_tree_node()->render_manager()->
-        GetOuterDelegateNode()->frame_tree()->root()->current_frame_host();
-  }
-
-  return static_cast<RenderWidgetHostViewBase*>(top_host->GetView());
+  RenderFrameHostImpl* current =
+      frame_proxy_in_parent_renderer_->frame_tree_node()->current_frame_host();
+  RenderFrameHostImpl* root = RootRenderFrameHost(current);
+  return static_cast<RenderWidgetHostViewBase*>(root->GetView());
 }
 
 RenderWidgetHostViewBase*
 CrossProcessFrameConnector::GetParentRenderWidgetHostView() {
-  FrameTreeNode* parent =
-      frame_proxy_in_parent_renderer_->frame_tree_node()->parent();
-
-  if (!parent &&
-      frame_proxy_in_parent_renderer_->frame_tree_node()
-          ->render_manager()
-          ->GetOuterDelegateNode()) {
-    parent = frame_proxy_in_parent_renderer_->frame_tree_node()
-                 ->render_manager()
-                 ->GetOuterDelegateNode()
-                 ->parent();
-  }
-
-  if (parent) {
-    return static_cast<RenderWidgetHostViewBase*>(
-        parent->current_frame_host()->GetView());
-  }
-
-  return nullptr;
+  RenderFrameHostImpl* current =
+      frame_proxy_in_parent_renderer_->frame_tree_node()->current_frame_host();
+  RenderFrameHostImpl* parent = ParentRenderFrameHost(current);
+  return parent ? static_cast<RenderWidgetHostViewBase*>(parent->GetView())
+                : nullptr;
 }
 
 void CrossProcessFrameConnector::EnableAutoResize(const gfx::Size& min_size,