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

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
===================================================================
--- content/renderer/render_thread_impl.cc	(revision 171370)
+++ content/renderer/render_thread_impl.cc	(working copy)
@@ -894,6 +894,13 @@
 
 scoped_ptr<base::SharedMemory> RenderThreadImpl::AllocateSharedMemory(
     uint32 size) {
+#if defined(OS_WIN)
+  scoped_ptr<base::SharedMemory> shared_memory(new base::SharedMemory);
+  if (!shared_memory->CreateAnonymous(size))

[jamesr, 2012/12/06 22:31:12]

content/renderer/pepper/pepper_plugin_delegate_impl creates shared memory in the
same was as this #else. Can we abstract this function int something shared and
use it from both RenderThreadImpl and PepperPluginDelegateImpl?

+    return scoped_ptr<base::SharedMemory>();
+
+  return scoped_ptr<base::SharedMemory>(shared_memory.release());
+#else
   base::SharedMemoryHandle handle;
   bool success;
   IPC::Message* message =
@@ -911,6 +918,7 @@
   if (!base::SharedMemory::IsHandleValid(handle))
     return scoped_ptr<base::SharedMemory>();
   return scoped_ptr<base::SharedMemory>(new base::SharedMemory(handle, false));
+#endif  // defined(OS_WIN)
 }
 
 int32 RenderThreadImpl::CreateViewCommandBuffer(