Add UMA metric: Startup.BrowserMainToRendererMain.

components/startup_metric_utils/browser/startup_metric_message_filter.cc

Index: components/startup_metric_utils/browser/startup_metric_message_filter.cc
diff --git a/components/startup_metric_utils/browser/startup_metric_message_filter.cc b/components/startup_metric_utils/browser/startup_metric_message_filter.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ddba4970e3a9d473b6d72824d473d8e929dd29b8
--- /dev/null
+++ b/components/startup_metric_utils/browser/startup_metric_message_filter.cc
@@ -0,0 +1,31 @@
+// Copyright 2015 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 "components/startup_metric_utils/browser/startup_metric_message_filter.h"
+
+#include "components/startup_metric_utils/browser/startup_metric_utils.h"
+#include "components/startup_metric_utils/common/startup_metric_messages.h"
+
+namespace startup_metric_utils {
+
+StartupMetricMessageFilter::StartupMetricMessageFilter()
+    : content::BrowserMessageFilter(StartupMetricMsgStart) {}
+
+bool StartupMetricMessageFilter::OnMessageReceived(
+    const IPC::Message& message) {
+  bool handled = true;
+  IPC_BEGIN_MESSAGE_MAP(StartupMetricMessageFilter, message)
+    IPC_MESSAGE_HANDLER(StartupMetricHostMsg_RecordRendererMainEntryTime,
+                        OnRecordRendererMainEntryTime)
+    IPC_MESSAGE_UNHANDLED(handled = false)
+  IPC_END_MESSAGE_MAP()
+  return handled;
+}
+
+void StartupMetricMessageFilter::OnRecordRendererMainEntryTime(
+    const base::Time& renderer_main_entry_time) {
+  RecordRendererMainEntryTime(renderer_main_entry_time);
+}
+
+}  // namespace startup_metric_utils