[content] Clean up FrameTreeNode::parent.

Convert a few places which can use FrameTreeNode::parent to use
RenderFrameHostImpl::GetParent instead.

This is more robust given that GetParent() never changes, while the
current RenderFrameHost in the parent FrameTreeNode might.

R=arthursonzogni@chromium.org,creis@chromium.org,lfg@chromium.org
CC=​alexmos@chromium.org,bfcache-bugs@chromium.org
BUG=1073269

Change-Id: I9b162f48825688f4b20c329721630d4c5cedb3e5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2161076Reviewed-by: Charlie Reis <creis@chromium.org>
Reviewed-by: Arthur Sonzogni <arthursonzogni@chromium.org>
Commit-Queue: Alexander Timin <altimin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#763314}

content/browser/frame_host/cross_process_frame_connector.cc

@@ -130,10 +130,11 @@ void CrossProcessFrameConnector::SetView(RenderWidgetHostViewChildFrame* view) {
 void CrossProcessFrameConnector::RenderProcessGone() {
   has_crashed_ = true;
 
-  FrameTreeNode* node = frame_proxy_in_parent_renderer_->frame_tree_node();
-  int process_id = node->current_frame_host()->GetProcess()->GetID();
-  for (node = node->parent(); node; node = node->parent()) {
-    if (node->current_frame_host()->GetProcess()->GetID() == process_id) {
+  RenderFrameHost* rfh =
+      frame_proxy_in_parent_renderer_->frame_tree_node()->current_frame_host();
+  int process_id = rfh->GetProcess()->GetID();
+  for (rfh = rfh->GetParent(); rfh; rfh = rfh->GetParent()) {
+    if (rfh->GetProcess()->GetID() == process_id) {
       // The crash will be already logged by the ancestor - ignore this crash in
       // the current instance of the CrossProcessFrameConnector.
       is_crash_already_logged_ = true;

content/browser/frame_host/frame_tree_node.cc

@@ -580,11 +580,11 @@ void FrameTreeNode::BeforeUnloadCanceled() {
 }
 
 bool FrameTreeNode::NotifyUserActivation() {
-  for (FrameTreeNode* node = this; node; node = node->parent()) {
-    if (!node->user_activation_state_.HasBeenActive() &&
-        node->current_frame_host())
-      node->current_frame_host()->DidReceiveFirstUserActivation();
-    node->user_activation_state_.Activate();
+  for (RenderFrameHostImpl* rfh = current_frame_host(); rfh;
+       rfh = rfh->GetParent()) {
+    if (!rfh->frame_tree_node()->user_activation_state_.HasBeenActive())
+      rfh->DidReceiveFirstUserActivation();
+    rfh->frame_tree_node()->user_activation_state_.Activate();
   }
   replication_state_.has_received_user_gesture = true;
 

content/browser/frame_host/render_frame_host_impl.h

@@ -554,6 +554,10 @@ class CONTENT_EXPORT RenderFrameHostImpl
   // will have the JS bindings enabled.
   void EnableMojoJsBindings();
 
+  // Returns true if this is a main RenderFrameHost. True if and only if this
+  // RenderFrameHost doesn't have a parent.
+  bool is_main_frame() const { return !parent_; }
+
   // Returns this RenderFrameHost's loading state. This method is only used by
   // FrameTreeNode. The proper way to check whether a frame is loading is to
   // call FrameTreeNode::IsLoading.
@@ -1853,12 +1857,12 @@ class CONTENT_EXPORT RenderFrameHostImpl
   // frames, it will return the current frame's view.
   RenderWidgetHostViewBase* GetViewForAccessibility();
 
-  // Returns the child FrameTreeNode if |child_frame_routing_id| is an
+  // Returns the child RenderFrameHostImpl if |child_frame_routing_id| is an
   // immediate child of this FrameTreeNode.  |child_frame_routing_id| is
   // considered untrusted, so the renderer process is killed if it refers to a
-  // FrameTreeNode that is not a child of this node.
-  FrameTreeNode* FindAndVerifyChild(int32_t child_frame_routing_id,
-                                    bad_message::BadMessageReason reason);
+  // RenderFrameHostImpl that is not a child of this node.
+  RenderFrameHostImpl* FindAndVerifyChild(int32_t child_frame_routing_id,
+                                          bad_message::BadMessageReason reason);
 
   // Returns a raw pointer to the Web Bluetooth Service owned by the frame. Used
   // for testing purposes only (see |TestRenderFrameHost|).

content/browser/frame_host/render_frame_proxy_host.cc

@@ -548,9 +548,8 @@ void RenderFrameProxyHost::OnRouteMessageEvent(
       // to the target frame before the postMessage, as sites might implicitly
       // be relying on this ordering.
       bool target_is_descendant_of_source = false;
-      for (FrameTreeNode* node = target_rfh->frame_tree_node(); node;
-           node = node->parent()) {
-        if (node == source_rfh->frame_tree_node()) {
+      for (RenderFrameHost* rfh = target_rfh; rfh; rfh = rfh->GetParent()) {
+        if (rfh == source_rfh) {
           target_is_descendant_of_source = true;
           break;
         }

content/browser/renderer_host/media/media_stream_ui_proxy.cc

@@ -48,14 +48,14 @@ void SetAndCheckAncestorFlag(MediaStreamRequest* request) {
     // RenderFrame destroyed before the request is handled?
     return;
   }
-  FrameTreeNode* node = rfh->frame_tree_node();
 
-  while (node->parent() != nullptr) {
-    if (!node->HasSameOrigin(*node->parent())) {
+  while (rfh->GetParent()) {
+    if (!rfh->GetLastCommittedOrigin().IsSameOriginWith(
+            rfh->GetParent()->GetLastCommittedOrigin())) {
       request->all_ancestors_have_same_origin =  false;
       return;
     }
-    node = node->parent();
+    rfh = rfh->GetParent();
   }
   request->all_ancestors_have_same_origin = true;
 }