Move Mailbox from cc to gpu, and its traits to gpu/ipc

gpu/command_buffer/common/mailbox.cc

+// Copyright 2013 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 "../common/mailbox.h"
+
+#include <string.h>
+
+#include "../common/logging.h"
+
+namespace gpu {
+
+Mailbox::Mailbox() {
+  memset(name, 0, sizeof(name));
+}
+
+bool Mailbox::IsZero() const {
+  for (size_t i = 0; i < arraysize(name); ++i) {
+    if (name[i])
+      return false;
+  }
+  return true;
+}
+
+void Mailbox::SetName(const int8* n) {
+  GPU_DCHECK(IsZero() || !memcmp(name, n, sizeof(name)));
+  memcpy(name, n, sizeof(name));
+}
+
+}  // namespace gpu