cc: Use maximum tiling contents scales for picture layer scale

cc/layer_impl.cc

Index: cc/layer_impl.cc
diff --git a/cc/layer_impl.cc b/cc/layer_impl.cc
index 98dc5599467fee9942b73a6314e6fdc2f28f938a..d00f21881be03245e60a3ff4891031a3addbece3 100644
--- a/cc/layer_impl.cc
+++ b/cc/layer_impl.cc
@@ -701,6 +701,19 @@ void LayerImpl::setContentsScale(float contentsScaleX, float contentsScaleY)
     noteLayerPropertyChanged();
 }
 
+void LayerImpl::calculateContentsScale(
+    float idealContentsScale,
+    float* contentsScaleX,
+    float* contentsScaleY,
+    gfx::Size* contentBounds)
+{
+    // Base LayerImpl has all of its content scales and content bounds pushed
+    // from its Layer during commit and just reuses those values as-is.
+    *contentsScaleX = this->contentsScaleX();
+    *contentsScaleY = this->contentsScaleY();
+    *contentBounds = this->contentBounds();
+}
+
 void LayerImpl::setScrollOffset(gfx::Vector2d scrollOffset)
 {
     if (m_scrollOffset == scrollOffset)