OOPIF: Specify previous sibling frames when creating RenderFrames.

When initializing a new renderer for an OOP frame, the current
behavior is to first create all the RenderFrameProxies, and then to
create the new RenderFrame, appending it as its parent's last child in
the frame tree.  This disregards the order of sibling frames and thus
may break indexed window access (e.g., window.frames[2]).

This CL passes the previous sibling's routing ID in the
FrameMsg_NewFrame message, so that the new frame can be inserted in
the correct place in the frame tree.  Note that we don't need to do
this for RenderFrameProxies, as those are already created in the
correct order (by CreateProxiesForSiteInstance) when initializing a
new renderer process.

Corresponding Blink CL: https://codereview.chromium.org/1119823003/

BUG=478792

Review URL: https://codereview.chromium.org/1113393004

Cr-Commit-Position: refs/heads/master@{#328384}

1 files changed, 4 insertions, 0 deletions

diff --git a/content/browser/frame_host/frame_tree_node.h b/content/browser/frame_host/frame_tree_node.h
index 4825082..4e98559 100644
--- a/content/browser/frame_host/frame_tree_node.h
+++ b/content/browser/frame_host/frame_tree_node.h
@@ -124,6 +124,10 @@ class CONTENT_EXPORT FrameTreeNode {
 
   bool IsDescendantOf(FrameTreeNode* other) const;
 
+  // Return the node immediately preceding this node in its parent's
+  // |children_|, or nullptr if there is no such node.
+  FrameTreeNode* PreviousSibling() const;
+
   // Returns true if this node is in a loading state.
   bool IsLoading() const;