Add stats collection for telemetry startup.warm.blank_page test.

components/html_viewer/stats_collection_observer.h

+// 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.
+
+#ifndef COMPONENTS_HTML_VIEWER_STATS_COLLECTION_OBSERVER_H_
+#define COMPONENTS_HTML_VIEWER_STATS_COLLECTION_OBSERVER_H_
+
+#include "base/time/time.h"
+#include "components/html_viewer/html_document.h"
+
+namespace html_viewer {
+
+// Collect timing information for page loads.
+class StatsCollectionObserver : public HTMLDocument::Observer {
+ public:
+  explicit StatsCollectionObserver(HTMLDocument* html_document);
+  ~StatsCollectionObserver() override;
+
+  // HTMLDocument::Observer implementation
+  void DidStartLoading() override;
+  void DidStopLoading() override;
+
+  // Timing for the page load start and stop.  These functions may return
+  // a null time value under various circumstances.
+  const base::Time& load_start_time() { return start_time_; }

[yzshen1, 2015/08/13 15:59:12]

Please use the same name for getter and the corresponding member variable.

[msw, 2015/08/14 23:20:35]

Removed.

+  const base::Time& load_stop_time() { return stop_time_; }
+
+ private:
+  base::Time start_time_;

[sky, 2015/08/12 23:54:36]

Shouldn't this use timeticks?

[msw, 2015/08/14 23:20:35]

Removed.

+  base::Time stop_time_;
+
+  DISALLOW_COPY_AND_ASSIGN(StatsCollectionObserver);
+};
+
+}  // namespace html_viewer
+
+#endif  // COMPONENTS_HTML_VIEWER_STATS_COLLECTION_OBSERVER_H_