[Tentaive patch for discussion] Add Purge+Suspend metrics as UMA.

content/browser/renderer_host/render_process_host_impl.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_BROWSER_RENDERER_HOST_RENDER_PROCESS_HOST_IMPL_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_PROCESS_HOST_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 166 matching lines @@
                                          int cdm_id) const override;
 #endif
   bool IsProcessBackgrounded() const override;
   void IncrementServiceWorkerRefCount() override;
   void DecrementServiceWorkerRefCount() override;
   void IncrementSharedWorkerRefCount() override;
   void DecrementSharedWorkerRefCount() override;
   void ForceReleaseWorkerRefCounts() override;
   bool IsWorkerRefCountDisabled() override;
   void PurgeAndSuspend() override;
+  const base::TimeTicks& GetLastPurgeAndSuspendTime() const override;
 
   mojom::RouteProvider* GetRemoteRouteProvider();
 
   // IPC::Sender via RenderProcessHost.
   bool Send(IPC::Message* msg) override;
 
   // IPC::Listener via RenderProcessHost.
   bool OnMessageReceived(const IPC::Message& msg) override;
   void OnChannelConnected(int32_t peer_pid) override;
   void OnChannelError() override;
@@ skipping 287 matching lines @@
   std::unique_ptr<base::Thread> in_process_renderer_;
 
   // True after Init() has been called. We can't just check channel_ because we
   // also reset that in the case of process termination.
   bool is_initialized_;
 
   // PlzNavigate
   // Stores the time at which the first call to Init happened.
   base::TimeTicks init_time_;
 
+  base::TimeTicks last_purge_and_suspend_time_;
+
   // Used to launch and terminate the process without blocking the UI thread.
   std::unique_ptr<ChildProcessLauncher> child_process_launcher_;
 
   // Messages we queue before the ChannelProxy is created.
   using MessageQueue = std::queue<std::unique_ptr<IPC::Message>>;
   MessageQueue queued_messages_;
 
   // The globally-unique identifier for this RPH.
   const int id_;
 
@@ skipping 105 matching lines @@
       instance_weak_factory_;
 
   base::WeakPtrFactory<RenderProcessHostImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderProcessHostImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_PROCESS_HOST_IMPL_H_