Add unit test and supporting code to test process overflow case.

chrome/browser/renderer_host/render_process_host.h

 // Copyright (c) 2009 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 CHROME_BROWSER_RENDERER_HOST_RENDER_PROCESS_HOST_H_
 #define CHROME_BROWSER_RENDERER_HOST_RENDER_PROCESS_HOST_H_
 
 #include <set>
 #include <string>
 
@@ skipping 239 matching lines @@
   // RenderProcessHost rather than creating a new one.
   static bool ShouldTryToUseExistingProcessHost();
 
   // Get an existing RenderProcessHost associated with the given profile, if
   // possible.  The renderer process is chosen randomly from suitable renderers
   // that share the same profile and type.
   // Returns NULL if no suitable renderer process is available, in which case
   // the caller is free to create a new renderer.
   static RenderProcessHost* GetExistingProcessHost(Profile* profile, Type type);
 
+  // Overrides the default heuristic for limiting the max renderer process
+  // count.  This is useful for unit testing process limit behaviors.
+  // A value of zero means to use the default heuristic.
+  static void SetMaxRendererProcessCount(size_t count);
+
  protected:
   // A proxy for our IPC::Channel that lives on the IO thread (see
   // browser_process.h)
   scoped_ptr<IPC::SyncChannel> channel_;
 
   // The registered listeners. When this list is empty or all NULL, we should
   // delete ourselves
   IDMap<IPC::Channel::Listener> listeners_;
 
   // The maximum page ID we've ever seen from the renderer process.
@@ skipping 35 matching lines @@
 // Factory object for RenderProcessHosts. Using this factory allows tests to
 // swap out a different one to use a TestRenderProcessHost.
 class RenderProcessHostFactory {
  public:
   virtual ~RenderProcessHostFactory() {}
   virtual RenderProcessHost* CreateRenderProcessHost(
       Profile* profile) const = 0;
 };
 
 #endif  // CHROME_BROWSER_RENDERER_HOST_RENDER_PROCESS_HOST_H_