[animations] Adds metrics for jank on selected layer animations

ui/compositor/animation_metrics_reporter_template.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 UI_ANIMATION_METRICS_REPORTER_TEMPLATE_H_
+#define UI_ANIMATION_METRICS_REPORTER_TEMPLATE_H_
+
+#include "base/metrics/histogram_macros.h"
+#include "ui/compositor/layer_animation_element.h"
+
+namespace ui {
+
+template <const char* name>
+class AnimationMetricsReporterTemplate : public AnimationMetricsReporter {
+  void Report(int value) override { UMA_HISTOGRAM_PERCENTAGE(name, value); }

[rkaplow, 2017/01/23 15:47:18]

you can't use the macros this way:
https://codesearch.chromium.org/chromium/src/base/metrics/histogram_macros.h?...

If you really want to set up the recording like this, you need to use what the
macros use, i.e. the base::LinearHistogram::FactoryGet. There's samples of this
use within the codebase

[varkha, 2017/01/24 00:18:57]

The intention here was exactly to make the strings a compile time static to
ensure that every code path that goes through a particular line ends with just
one histogram instance. Unfortunately only some compilers allow string
parameters in compile time templates so I had to go back to subclassing (similar
to
https://cs.chromium.org/chromium/src/cc/scheduler/compositor_timing_history.c...)

+};
+
+}  // namespace ui
+
+#endif  // UI_ANIMATION_METRICS_REPORTER_TEMPLATE_H_