GPU: 'Pass' SharedMemory when possible.

content/common/gpu/gpu_command_buffer_stub.cc

Index: content/common/gpu/gpu_command_buffer_stub.cc
diff --git a/content/common/gpu/gpu_command_buffer_stub.cc b/content/common/gpu/gpu_command_buffer_stub.cc
index 8bccd2abd2f66732ce60175a50a2f87802dbc42a..ef6a45a2e1916e21ed9fc8ba7611a40ea9f23a7c 100644
--- a/content/common/gpu/gpu_command_buffer_stub.cc
+++ b/content/common/gpu/gpu_command_buffer_stub.cc
@@ -686,9 +686,18 @@ void GpuCommandBufferStub::OnRegisterTransferBuffer(
     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) {