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

chrome/renderer/print_web_view_helper.cc

 // 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.
 
 #include "chrome/renderer/print_web_view_helper.h"
 
 #include <string>
 
 #include "base/auto_reset.h"
 #include "base/command_line.h"
@@ skipping 1380 matching lines @@
   if (print_pages_params_->params.selection_only)
     return CopyAndPrint(frame);
   return PrintPages(frame, node);
 }
 
 #if defined(OS_POSIX)
 bool PrintWebViewHelper::CopyMetafileDataToSharedMem(
     printing::Metafile* metafile,
     base::SharedMemoryHandle* shared_mem_handle) {
   uint32 buf_size = metafile->GetDataSize();
-  base::SharedMemoryHandle mem_handle =
-      content::RenderThread::Get()->HostAllocateSharedMemoryBuffer(buf_size);
-  if (base::SharedMemory::IsHandleValid(mem_handle)) {
-    base::SharedMemory shared_buf(mem_handle, false);
-    if (shared_buf.Map(buf_size)) {
-      metafile->GetData(shared_buf.memory(), buf_size);
-      shared_buf.GiveToProcess(base::GetCurrentProcessHandle(),
-                               shared_mem_handle);
+  scoped_ptr<base::SharedMemory> shared_buf(
+      content::RenderThread::Get()->HostAllocateSharedMemoryBuffer(
+          buf_size).release());
+
+  if (shared_buf.get()) {
+    if (shared_buf->Map(buf_size)) {
+      metafile->GetData(shared_buf->memory(), buf_size);
+      shared_buf->GiveToProcess(base::GetCurrentProcessHandle(),
+                                shared_mem_handle);
       return true;
     }
   }
   NOTREACHED();
   return false;
 }
 #endif  // defined(OS_POSIX)
 
 bool PrintWebViewHelper::IsScriptInitiatedPrintTooFrequent(
     WebKit::WebFrame* frame) {
@@ skipping 335 matching lines @@
   DCHECK(IsRendering());
   return prep_frame_view_->GetPrintCanvasSize();
 }
 
 void PrintWebViewHelper::PrintPreviewContext::ClearContext() {
   prep_frame_view_.reset();
   metafile_.reset();
   pages_to_render_.clear();
   error_ = PREVIEW_ERROR_NONE;
 }