Pass accurate contentsScale to LayerImpl.

cc/contents_scaling_layer.cc

Index: cc/contents_scaling_layer.cc
diff --git a/cc/contents_scaling_layer.cc b/cc/contents_scaling_layer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..fcfaebd6960e00a07b5c2a4e3f121efcf6c26faf
--- /dev/null
+++ b/cc/contents_scaling_layer.cc
@@ -0,0 +1,30 @@
+// Copyright 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 "config.h"
+
+#include "cc/contents_scaling_layer.h"
+
+namespace cc {
+
+ContentsScalingLayer::ContentsScalingLayer()
+    : m_contentsScale(1.0) {
+}
+
+ContentsScalingLayer::~ContentsScalingLayer() {
+}
+
+IntSize ContentsScalingLayer::contentBounds() const {
+  return IntSize(ceil(bounds().width() * contentsScaleX()),
+                 ceil(bounds().height() * contentsScaleY()));
+}
+
+void ContentsScalingLayer::setContentsScale(float contentsScale) {
+  if (m_contentsScale == contentsScale)
+    return;
+  m_contentsScale = contentsScale;
+  setNeedsDisplay();
+}
+
+}  // namespace cc