GPU: 'Pass' SharedMemory when possible.

content/common/gpu/gpu_command_buffer_stub.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 "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/hash.h"
 #include "base/memory/shared_memory.h"
@@ skipping 668 matching lines @@
 
   if (pre_state.get_offset != post_state.get_offset)
     ReportState();
 }
 
 void GpuCommandBufferStub::OnRegisterTransferBuffer(
     int32 id,
     base::SharedMemoryHandle transfer_buffer,
     uint32 size) {
   TRACE_EVENT0("gpu", "GpuCommandBufferStub::OnRegisterTransferBuffer");
-  base::SharedMemory shared_memory(transfer_buffer, false);
+
+  // Take ownership of the memory and map it into this process.
+  // This validates the size.
+  scoped_ptr<base::SharedMemory> shared_memory(
+      new base::SharedMemory(transfer_buffer, false));
+  if (!shared_memory->Map(size)) {
+    DVLOG(0) << "Failed to map shared memory.";
+    return;
+  }
+
   if (command_buffer_)
-    command_buffer_->RegisterTransferBuffer(id, &shared_memory, size);
+    command_buffer_->RegisterTransferBuffer(id, shared_memory.Pass(), size);
 }
 
 void GpuCommandBufferStub::OnDestroyTransferBuffer(int32 id) {
   TRACE_EVENT0("gpu", "GpuCommandBufferStub::OnDestroyTransferBuffer");
 
   if (command_buffer_)
     command_buffer_->DestroyTransferBuffer(id);
 }
 
 void GpuCommandBufferStub::OnGetTransferBuffer(
@@ skipping 275 matching lines @@
   if (decoder_)
     decoder_->LoseContext(GL_UNKNOWN_CONTEXT_RESET_ARB);
   command_buffer_->SetParseError(gpu::error::kLostContext);
 }
 
 uint64 GpuCommandBufferStub::GetMemoryUsage() const {
   return GetMemoryManager()->GetClientMemoryUsage(this);
 }
 
 }  // namespace content