Do not convert from RectF to Rect by flooring.

ui/gfx/safe_floor_ceil.cc

Index: ui/gfx/safe_floor_ceil.cc
diff --git a/ui/gfx/safe_floor_ceil.cc b/ui/gfx/safe_floor_ceil.cc
new file mode 100644
index 0000000000000000000000000000000000000000..3932e482f60030a4002f771a8ea0e48e7adb6cef
--- /dev/null
+++ b/ui/gfx/safe_floor_ceil.cc
@@ -0,0 +1,29 @@
+// 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 <cmath>
+#include <limits>
+
+namespace gfx {
+
+int ClampToInt(float value) {
+  if (value != value)
+     return 0; // no int NaN.
+  if (value > std::numeric_limits<int>::max())
+    return std::numeric_limits<int>::max();
+  if (value < std::numeric_limits<int>::min())
+    return std::numeric_limits<int>::max();
+  return static_cast<int>(value);
+}
+
+int ToFlooredInt(float value) {
+  return ClampToInt(std::floor(value));
+}
+
+int ToCeiledInt(float value) {
+  return ClampToInt(std::ceil(value));
+}
+
+}  // namespace gfx
+