cc: Add UMA stats for record and raster time.

cc/base/histograms.cc

+// 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 "cc/base/histograms.h"
+
+#include <algorithm>
+#include <limits>
+
+#include "base/float_util.h"
+#include "base/numerics/safe_conversions.h"
+
+namespace cc {
+
+// Minimum elapsed time of 1us to limit weighting of fast calls.
+static const int64 kMinimumTimeMicroseconds = 1;
+
+ScopedUMAHistogramAreaTimerBase::ScopedUMAHistogramAreaTimerBase() : area_(0) {
+}
+
+ScopedUMAHistogramAreaTimerBase::~ScopedUMAHistogramAreaTimerBase() {
+}
+
+void ScopedUMAHistogramAreaTimerBase::GetHistogramValues(
+    Sample* time_microseconds,
+    Sample* pixels_per_ms) const {
+  GetHistogramValues(timer_.Elapsed(),
+                     area_.ValueOrDefault(std::numeric_limits<int>::max()),
+                     time_microseconds, pixels_per_ms);
+}
+
+// static
+void ScopedUMAHistogramAreaTimerBase::GetHistogramValues(
+    base::TimeDelta elapsed,
+    int area,
+    Sample* time_microseconds,
+    Sample* pixels_per_ms) {
+  elapsed = std::max(
+      elapsed, base::TimeDelta::FromMicroseconds(kMinimumTimeMicroseconds));
+  double area_per_time = area / elapsed.InMillisecondsF();
+  DCHECK(!base::IsNaN(area_per_time));
+  *time_microseconds = base::saturated_cast<Sample>(elapsed.InMicroseconds());
+  *pixels_per_ms = base::saturated_cast<Sample>(area_per_time);
+}
+
+}  // namespace cc