Content API changes to improve DOM stitching in ThreatDetails code.

content/public/browser/render_frame_host.h

Index: content/public/browser/render_frame_host.h
diff --git a/content/public/browser/render_frame_host.h b/content/public/browser/render_frame_host.h
index a3d5490fd1009ce3139b47a3248c2aa4eb40e5dc..5b23cbaf390b89adde72f8cc0045c88339e730ce 100644
--- a/content/public/browser/render_frame_host.h
+++ b/content/public/browser/render_frame_host.h
@@ -49,6 +49,9 @@ struct FileChooserFileInfo;
 class CONTENT_EXPORT RenderFrameHost : public IPC::Listener,
                                        public IPC::Sender {
  public:
+  // Constant used to denote that a lookup of a FrameTreeNode ID has failed.
+  static const int kNoFrameTreeNodeId = -1;
+
   // Returns the RenderFrameHost given its ID and the ID of its render process.
   // Returns nullptr if the IDs do not correspond to a live RenderFrameHost.
   static RenderFrameHost* FromID(int render_process_id, int render_frame_id);
@@ -63,6 +66,11 @@ class CONTENT_EXPORT RenderFrameHost : public IPC::Listener,
   // Returns a RenderFrameHost given its accessibility tree ID.
   static RenderFrameHost* FromAXTreeID(int ax_tree_id);
 
+  // Returns the FrameTreeNode ID corresponding to the specified |process_id|
+  // and |routing_id|. This routing ID pair may represent a placeholder for
+  // frame that is currently rendered in a different process than |process_id|.
+  static int GetFrameTreeNodeIdForRoutingId(int process_id, int routing_id);
+
   ~RenderFrameHost() override {}
 
   // Returns the route id for this frame.