Buffer cross frame paint timing updates.

chrome/common/page_load_metrics/test/weak_mock_timer.h

+// Copyright 2017 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 CHROME_COMMON_PAGE_LOAD_METRICS_TEST_WEAK_MOCK_TIMER_H_
+#define CHROME_COMMON_PAGE_LOAD_METRICS_TEST_WEAK_MOCK_TIMER_H_
+
+#include "base/memory/weak_ptr.h"
+#include "base/timer/mock_timer.h"
+
+namespace page_load_metrics {

[Charlie Harrison, 2017/05/30 14:49:08]

We didn't talk about this before but it is also not uncommon to have an
additional "testing" namespace. Up to you if you want it, I don't care either
way.

[Bryan McQuade, 2017/05/30 15:30:23]

Ah, I grepped around until chrome/common and didn't see this much, so decided
not to, but you're right that this appears to be more common in chrome/browser.
namespace test seems the most common so will use that.

+
+// WeakMockTimer is a MockTimer that allows clients to keep WeakPtr<>s to it.
+class WeakMockTimer : public base::MockTimer,
+                      public base::SupportsWeakPtr<WeakMockTimer> {
+ public:
+  WeakMockTimer();
+};

[Charlie Harrison, 2017/05/30 14:49:08]

Do we want to DISALLOW_COPY_AND_ASSIGN to these timers/ timer providers? I don't
think we need to copy them anywhere.

[Bryan McQuade, 2017/05/30 15:30:23]

done

+
+// WeakMockTimerProvider is a testing helper class that test classes can inherit
+// from to provide basic MockTimer tracking capabilities.
+class WeakMockTimerProvider {
+ public:
+  WeakMockTimerProvider();
+  virtual ~WeakMockTimerProvider();
+
+  base::MockTimer* GetMockTimer() const;
+  void SetMockTimer(base::WeakPtr<WeakMockTimer> timer);
+
+ private:
+  base::WeakPtr<WeakMockTimer> timer_;
+};
+
+}  // namespace page_load_metrics
+
+#endif  // CHROME_COMMON_PAGE_LOAD_METRICS_TEST_WEAK_MOCK_TIMER_H_