Renderer process can allocate anonymous shared memory without help from browser process on Windows.

content/public/renderer/render_thread.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_RENDERER_RENDER_THREAD_H_
 #define CONTENT_PUBLIC_RENDERER_RENDER_THREAD_H_
 
 #include "base/basictypes.h"
 #include "base/shared_memory.h"
 #include "content/common/content_export.h"
@@ skipping 64 matching lines @@
   virtual void WidgetRestored() = 0;
 
   // We initialize WebKit as late as possible. Call this to force
   // initialization.
   virtual void EnsureWebKitInitialized() = 0;
 
   // Helper function to send over a string to be recorded by user metrics
   virtual void RecordUserMetrics(const std::string& action) = 0;
 
   // Asks the host to create a block of shared memory for the renderer.
-  // The shared memory handle allocated by the host is returned back.
-  virtual base::SharedMemoryHandle HostAllocateSharedMemoryBuffer(
+  // The shared memory allocated by the host is returned back.
+  virtual scoped_ptr<base::SharedMemory> HostAllocateSharedMemoryBuffer(
       uint32 buffer_size) = 0;
 
   // Registers the given V8 extension with WebKit.
   virtual void RegisterExtension(v8::Extension* extension) = 0;
 
   // Schedule a call to IdleHandler with the given initial delay.
   virtual void ScheduleIdleHandler(int64 initial_delay_ms) = 0;
 
   // A task we invoke periodically to assist with idle cleanup.
   virtual void IdleHandler() = 0;
@@ skipping 14 matching lines @@
   virtual void PreCacheFont(const LOGFONT& log_font) = 0;
 
   // Release cached font.
   virtual void ReleaseCachedFonts() = 0;
 #endif
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_RENDERER_RENDER_THREAD_H_