Pipe the devTools FrameId from blink into the browser for headless

headless/lib/browser/headless_browser_context_impl.h

Index: headless/lib/browser/headless_browser_context_impl.h
diff --git a/headless/lib/browser/headless_browser_context_impl.h b/headless/lib/browser/headless_browser_context_impl.h
index 688244917936123d7ac9e369501f85f4135758bb..492de2b7bd89ee22099de7c8ee39acd963510252 100644
--- a/headless/lib/browser/headless_browser_context_impl.h
+++ b/headless/lib/browser/headless_browser_context_impl.h
@@ -42,9 +42,17 @@ class HeadlessBrowserContextImpl : public HeadlessBrowserContext,
   std::vector<HeadlessWebContents*> GetAllWebContents() override;
   HeadlessWebContents* GetWebContentsForDevToolsAgentHostId(
       const std::string& devtools_agent_host_id) override;
+  int GetFrameTreeNodeId(int render_process_id,
+                         int render_frame_id) const override;
   void Close() override;
   const std::string& Id() const override;
 
+  void SetFrameTreeNodeId(int render_process_id,
+                          int render_frame_id,
+                          int frame_tree_node_id);
+
+  void RemoveFrameTreeNode(int render_process_id, int render_frame_id);
+
   // BrowserContext implementation:
   std::unique_ptr<content::ZoomLevelDelegate> CreateZoomLevelDelegate(
       const base::FilePath& partition_path) override;
@@ -98,6 +106,9 @@ class HeadlessBrowserContextImpl : public HeadlessBrowserContext,
   std::unordered_map<std::string, std::unique_ptr<HeadlessWebContents>>
       web_contents_map_;
 
+  mutable base::Lock frame_tree_node_map_lock_;  // Guards frame_tree_node_map_
+  std::map<std::pair<int, int>, int> frame_tree_node_map_;
+
   std::unique_ptr<content::PermissionManager> permission_manager_;
 
   std::string id_;