Task Manager should listen to WebContentsObserver::RenderFrameCreated.

content/public/browser/render_process_host.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_PUBLIC_BROWSER_RENDER_PROCESS_HOST_H_
 #define CONTENT_PUBLIC_BROWSER_RENDER_PROCESS_HOST_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 338 matching lines @@
 
   // Whether this process is locked out from ever being reused for sites other
   // than the ones it currently has.
   virtual void SetIsNeverSuitableForReuse() = 0;
   virtual bool MayReuseHost() = 0;
 
   // Returns the current number of active views in this process.  Excludes
   // any RenderViewHosts that are swapped out.
   size_t GetActiveViewCount();
 
+  // Posts |task|, if this RenderProcessHost is ready or when it becomes ready
+  // (see RenderProcessHost::IsReady method).  The |task| might not run at all
+  // (e.g. if |render_process_host| is destroyed before becoming ready).  This
+  // function can only be called on the browser's UI thread (and the |task| will
+  // be posted back on the UI thread).
+  void PostTaskWhenProcessIsReady(base::OnceClosure task);

[ncarter (slow), 2017/05/12 21:56:02]

I bet we could implement RenderViewHostImpl::PostRenderViewReady() in terms of
this, and delete some code out of RenderViewHostImpl.

[Łukasz Anforowicz, 2017/05/16 16:37:25]

Good idea.  Done.

+
   // Static management functions -----------------------------------------------
 
   // Flag to run the renderer in process.  This is primarily
   // for debugging purposes.  When running "in process", the
   // browser maintains a single RenderProcessHost which communicates
   // to a RenderProcess which is instantiated in the same process
   // with the Browser.  All IPC between the Browser and the
   // Renderer is the same, it's just not crossing a process boundary.
 
   static bool run_renderer_in_process();
@@ skipping 38 matching lines @@
   static void SetMaxRendererProcessCount(size_t count);
 
   // Returns the current maximum number of renderer process hosts kept by the
   // content module.
   static size_t GetMaxRendererProcessCount();
 };
 
 }  // namespace content.
 
 #endif  // CONTENT_PUBLIC_BROWSER_RENDER_PROCESS_HOST_H_