Enable spare RenderProcessHost to be preinitialized.

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 96 matching lines @@
 // because all the IPCs from the RenderViews (renderer) will only ever be able
 // to access the partition they are assigned to.
 class CONTENT_EXPORT RenderProcessHostImpl
     : public RenderProcessHost,
       public ChildProcessLauncher::Client,
       public ui::GpuSwitchingObserver,
       public NON_EXPORTED_BASE(mojom::RouteProvider),
       public NON_EXPORTED_BASE(mojom::AssociatedInterfaceProvider),
       public NON_EXPORTED_BASE(mojom::RendererHost) {
  public:
-  RenderProcessHostImpl(BrowserContext* browser_context,
-                        StoragePartitionImpl* storage_partition_impl,
-                        bool is_for_guests_only);
+  // Use the spare RenderProcessHost if it exists, or create a new one. This
+  // should be the usual way to get a new RenderProcessHost.
+  static RenderProcessHost* CreateOrUseSpareRenderProcessHost(
+      BrowserContext* browser_context,
+      StoragePartitionImpl* storage_partition_impl,
+      bool is_for_guests_only);
+
+  // Create a new RenderProcessHost. In most cases
+  // CreateOrUseSpareRenderProcessHost, above, should be used instead.
+  static RenderProcessHost* CreateRenderProcessHost(
+      BrowserContext* browser_context,
+      StoragePartitionImpl* storage_partition_impl,
+      bool is_for_guests_only);
+
   ~RenderProcessHostImpl() override;
 
   // RenderProcessHost implementation (public portion).
   bool Init() override;
   void EnableSendQueue() override;
   int GetNextRoutingID() override;
   void AddRoute(int32_t routing_id, IPC::Listener* listener) override;
   void RemoveRoute(int32_t routing_id) override;
   void AddObserver(RenderProcessHostObserver* observer) override;
   void RemoveObserver(RenderProcessHostObserver* observer) override;
@@ skipping 200 matching lines @@
   // RenderProcessHosts.
   static void AddExpectedNavigationToSite(
       BrowserContext* browser_context,
       RenderProcessHost* render_process_host,
       const GURL& site_url);
   static void RemoveExpectedNavigationToSite(
       BrowserContext* browser_context,
       RenderProcessHost* render_process_host,
       const GURL& site_url);
 
+  // Return the spare RenderProcessHost, if it exists. There is at most one
+  // globally-used spare RenderProcessHost at any time.
+  static RenderProcessHost* GetSpareRenderProcessHostForTesting();
+
  protected:
   // A proxy for our IPC::Channel that lives on the IO thread.
   std::unique_ptr<IPC::ChannelProxy> channel_;
 
   // True if fast shutdown has been performed on this RPH.
   bool fast_shutdown_started_;
 
   // True if we've posted a DeleteTask and will be deleted soon.
   bool deleting_soon_;
 
 #ifndef NDEBUG
   // True if this object has deleted itself.
   bool is_self_deleted_;
 #endif
 
   // The count of currently swapped out but pending RenderViews.  We have
   // started to swap these in, so the renderer process should not exit if
   // this count is non-zero.
   int32_t pending_views_;
 
  private:
   friend class ChildProcessLauncherBrowserTest_ChildSpawnFail_Test;
   friend class VisitRelayingRenderProcessHost;
   class ConnectionFilterController;
   class ConnectionFilterImpl;
 
+  // Use CreateRenderProcessHost() instead of calling this constructor
+  // directly.
+  RenderProcessHostImpl(BrowserContext* browser_context,
+                        StoragePartitionImpl* storage_partition_impl,
+                        bool is_for_guests_only);
+
   // Initializes a new IPC::ChannelProxy in |channel_|, which will be connected
   // to the next child process launched for this host, if any.
   void InitializeChannelProxy();
 
   // Resets |channel_|, removing it from the attachment broker if necessary.
   // Always call this in lieu of directly resetting |channel_|.
   void ResetChannelProxy();
 
   // Creates and adds the IO thread message filters.
   void CreateMessageFilters();
@@ skipping 337 matching lines @@
   FrameSinkProviderImpl frame_sink_provider_;
 
   base::WeakPtrFactory<RenderProcessHostImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderProcessHostImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_PROCESS_HOST_IMPL_H_