Pass accurate contentsScale to LayerImpl.

cc/image_layer.cc

Index: cc/image_layer.cc
diff --git a/cc/image_layer.cc b/cc/image_layer.cc
index e1620073e46a3db9c3e059e697decb0e347797e1..3c1712eeffc280d3af0e5ae3372965442ee9bb33 100644
--- a/cc/image_layer.cc
+++ b/cc/image_layer.cc
@@ -150,10 +150,18 @@ bool ImageLayer::drawsContent() const
     return !m_bitmap.isNull() && TiledLayer::drawsContent();
 }
 
-bool ImageLayer::needsContentsScale() const
+float ImageLayer::contentsScaleX() const
 {
-    // Contents scale is not need for image layer because this can be done in compositor more efficiently.
-    return false;
+    if (bounds().isEmpty() || contentBounds().isEmpty())
+        return 1;
+    return static_cast<float>(m_bitmap.width()) / bounds().width();
+}
+
+float ImageLayer::contentsScaleY() const
+{
+    if (bounds().isEmpty() || contentBounds().isEmpty())
+        return 1;
+    return static_cast<float>(m_bitmap.height()) / bounds().height();
 }
 
 }