Creating utility for converting TimeTicks to WebKit double and use it in the Chrome compositor.

webkit/renderer/compositor_bindings/webkit_time_unittest.cc

+// Copyright (c) 2012 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 "webkit/renderer/compositor_bindings/webkit_time.h"
+
+#include <cmath>
+#include <limits>
+
+#include "base/time/time.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+using base::TimeTicks;
+
+TEST(WebKitTime, Conversion) {
+  double double_null = 0;
+  double double_max = std::numeric_limits<double>::max();
+  double double_min = std::numeric_limits<double>::lowest();
+  double double_positive_inf = std::numeric_limits<double>::infinity();
+  double double_negative_inf = -std::numeric_limits<double>::infinity();
+
+  base::TimeTicks ticks_null = base::TimeTicks();
+  base::TimeTicks ticks_min =
+      base::TimeTicks::FromInternalValue(std::numeric_limits<int64>::min());
+  base::TimeTicks ticks_max =
+      base::TimeTicks::FromInternalValue(std::numeric_limits<int64>::max());
+
+  EXPECT_EQ(ticks_null, webkit::FromWebKitTime(double_null));
+  EXPECT_EQ(ticks_max, webkit::FromWebKitTime(double_max));
+  EXPECT_EQ(ticks_min, webkit::FromWebKitTime(double_min));
+  EXPECT_EQ(ticks_max, webkit::FromWebKitTime(double_positive_inf));
+  EXPECT_EQ(ticks_min, webkit::FromWebKitTime(double_negative_inf));
+
+  EXPECT_EQ(double_null, webkit::ToWebKitTime(ticks_null));
+  EXPECT_EQ(double_negative_inf, webkit::ToWebKitTime(ticks_min));
+  EXPECT_EQ(double_positive_inf, webkit::ToWebKitTime(ticks_max));
+
+  // Round trip some values
+  // Outside of 2**53 the int64->double->int64 round trip isn't exact.
+  for (int i = -63; i < 53; i++) {
+    if (!i)
+      continue;
+
+    SCOPED_TRACE(i);
+    double i_abs = abs(static_cast<double>(i));
+
+    base::TimeTicks ticks_value = base::TimeTicks::FromInternalValue(
+        static_cast<int64>((i / i_abs) * pow(2.0, i_abs)));
+    EXPECT_EQ(webkit::FromWebKitTime(webkit::ToWebKitTime(ticks_value)),
+              ticks_value);
+
+    double double_value = (i / i_abs) * pow(2.0, i_abs) / 1e6;
+    EXPECT_EQ(webkit::ToWebKitTime(webkit::FromWebKitTime(double_value)),
+              double_value);
+  }
+}