cc: Reland "Add UMA stats for record and raster time."

cc/base/histograms_unittest.cc

Index: cc/base/histograms_unittest.cc
diff --git a/cc/base/histograms_unittest.cc b/cc/base/histograms_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..19bdb09bd7b406d07b6fb50c37423fc3e573d489
--- /dev/null
+++ b/cc/base/histograms_unittest.cc
@@ -0,0 +1,65 @@
+// 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 <limits>
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+using base::TimeDelta;
+using Sample = base::HistogramBase::Sample;
+
+namespace cc {
+
+class ScopedUMAHistogramAreaTimerBaseTest : public ::testing::Test {
+ protected:
+  void ExpectValidHistogramValues(base::TimeDelta elapsed,
+                                  int area,
+                                  Sample expected_time_microseconds,
+                                  Sample expected_pixels_per_ms) {
+    Sample time_microseconds;
+    Sample pixels_per_ms;
+    ScopedUMAHistogramAreaTimerBase::GetHistogramValues(
+        elapsed, area, &time_microseconds, &pixels_per_ms);
+    EXPECT_EQ(expected_time_microseconds, time_microseconds);
+    EXPECT_EQ(expected_pixels_per_ms, pixels_per_ms);
+  }
+};
+
+namespace {
+
+TEST_F(ScopedUMAHistogramAreaTimerBaseTest, CommonCase) {
+  ExpectValidHistogramValues(TimeDelta::FromMicroseconds(500), 1000, 500, 2000);
+  ExpectValidHistogramValues(TimeDelta::FromMicroseconds(300), 1000, 300, 3333);
+}
+
+TEST_F(ScopedUMAHistogramAreaTimerBaseTest, ZeroArea) {
+  ExpectValidHistogramValues(TimeDelta::FromMicroseconds(500), 0, 500, 0);
+}
+
+TEST_F(ScopedUMAHistogramAreaTimerBaseTest, ZeroTime) {
+  // 1M pixels/ms, since the time is limited to at least 1us.
+  ExpectValidHistogramValues(TimeDelta(), 1000, 1, 1000000);
+}
+
+TEST_F(ScopedUMAHistogramAreaTimerBaseTest, ZeroTimeAndArea) {
+  ExpectValidHistogramValues(TimeDelta(), 0, 1, 0);
+}
+
+TEST_F(ScopedUMAHistogramAreaTimerBaseTest, VeryLargeTime) {
+  ExpectValidHistogramValues(TimeDelta::FromHours(24), 1000,
+                             std::numeric_limits<Sample>::max(), 0);
+}
+
+TEST_F(ScopedUMAHistogramAreaTimerBaseTest, VeryLargeArea) {
+  ExpectValidHistogramValues(TimeDelta::FromMicroseconds(500), 1000000000, 500,
+                             2000000000);
+  ExpectValidHistogramValues(TimeDelta::FromMicroseconds(1000),
+                             std::numeric_limits<int>::max(), 1000,
+                             std::numeric_limits<Sample>::max());
+}
+
+}  // namespace
+}  // namespace cc