Pipe the devTools FrameId from blink into the browser for headless

headless/public/headless_web_contents.h

Index: headless/public/headless_web_contents.h
diff --git a/headless/public/headless_web_contents.h b/headless/public/headless_web_contents.h
index 031045f0e964221915b32bcbeddf7523912b10ea..30e9de5058a046fc5bdf84f3dd10236482394169 100644
--- a/headless/public/headless_web_contents.h
+++ b/headless/public/headless_web_contents.h
@@ -77,10 +77,16 @@ class HEADLESS_EXPORT HeadlessWebContents {
 
   // Returns the frame tree node id associated with the |devtools_agent_host_id|
   // if any.
+  // TODO(alexclarke): Remove this, it doesn't work as expected.
   virtual bool GetFrameTreeNodeIdForDevToolsAgentHostId(
       const std::string& devtools_agent_host_id,
       int* frame_tree_node_id) const = 0;
 
+  // Returns the devtools frame id corresponding to the |frame_tree_node_id|, if
+  // any.  Note this only works after we have received the data from blink.

[Sami, 2017/04/24 19:54:05]

nit: "after we have received the data from blink" is a little hard to interpret
at this level. Is there a notification we have to wait for?

[alex clarke (OOO till 29th), 2017/04/25 15:01:03]

Done.

+  virtual std::string GetDevToolsFrameIdForFrameTreeNodeId(

[Sami, 2017/04/24 19:54:05]

Could we put this (and the new method on HeadlessWebContents) just on the
corresponding impls instead of making them part of the public API? The reason is
that there isn't really a way to use this just through public headless API
(e.g., the render process ids or frame ids aren't exposed anywhere), and I
wouldn't want to encourage folks to start depending on random bits of content/
to get that data.

[alex clarke (OOO till 29th), 2017/04/25 15:01:03]

Done.

+      int frame_tree_node_id) const = 0;
+
  private:
   friend class HeadlessWebContentsImpl;
   HeadlessWebContents() {}