Pipe the devTools FrameId from blink into the browser for headless

headless/lib/browser/headless_web_contents_impl.h

Index: headless/lib/browser/headless_web_contents_impl.h
diff --git a/headless/lib/browser/headless_web_contents_impl.h b/headless/lib/browser/headless_web_contents_impl.h
index e578e8aede79e69bde39ea96086563e463d7753d..771a5faa0b75d3b221f884e46361763125a326df 100644
--- a/headless/lib/browser/headless_web_contents_impl.h
+++ b/headless/lib/browser/headless_web_contents_impl.h
@@ -100,6 +100,14 @@ class HEADLESS_EXPORT HeadlessWebContentsImpl
     return window_tree_host_.get();
   }
 
+  // Returns the devtools frame id corresponding to the |frame_tree_node_id|, if
+  // any.  Note this relies on an IPC sent from blink during navigation.
+  std::string GetUntrustedDevToolsFrameIdForFrameTreeNodeId(
+      int process_id,
+      int frame_tree_node_id) const;
+
+  int GetRenderProcessId() const;

[Charlie Reis, 2017/04/26 19:52:56]

A WebContents can have multiple processes, so we shouldn't introduce a new API
suggesting it has only one.  (WebContents::GetRenderProcessHost() is on its way
out in https://crbug.com/666525.)

We should at least rename it to GetMainFrameProcessId() (and implement it using
GetMainFrame()->GetProcess()->GetID()).

Or actually, this appears to only be used in tests?  Maybe there's a way to
avoid exposing it, or make it specific to tests?

[alex clarke (OOO till 29th), 2017/04/27 08:49:44]

Done.

+
  private:
   // Takes ownership of |web_contents|.
   HeadlessWebContentsImpl(content::WebContents* web_contents,