Pass accurate contentsScale to LayerImpl.

cc/damage_tracker.cc

Index: cc/damage_tracker.cc
diff --git a/cc/damage_tracker.cc b/cc/damage_tracker.cc
index 4c27d4d559e30607e45741e232aabd8879e75ee1..d36cbc00b02553cceb667c56e9a3a3ae29c812d4 100644
--- a/cc/damage_tracker.cc
+++ b/cc/damage_tracker.cc
@@ -268,9 +268,7 @@ void DamageTracker::extendDamageForLayer(LayerImpl* layer, FloatRect& targetDama
         // If the layer properties havent changed, then the the target surface is only
         // affected by the layer's update area, which could be empty.
         FloatRect updateContentRect = layer->updateRect();
-        float widthScale = layer->contentBounds().width() / static_cast<float>(layer->bounds().width());
-        float heightScale = layer->contentBounds().height() / static_cast<float>(layer->bounds().height());
-        updateContentRect.scale(widthScale, heightScale);
+        updateContentRect.scale(layer->contentsScaleX(), layer->contentsScaleY());

[danakj, 2012/10/29 20:06:51]

Can we use Layer::layerRectToContentRect() here? The current code isn't doing
toEnclosingIntRect, but it should be anyhow.

[wangxianzhu, 2012/10/30 02:14:21]

Done. However, I'm wondering if enclosingIntRect() is strictly necessary here
because all later calculations are using FloatRect.

[danakj, 2012/10/30 15:56:19]

Right, but part of a pixel can't be invalid, so I think it makes sense to do it
here as well. Thanks for the fixes!

 
         FloatRect updateRectInTargetSpace = MathUtil::mapClippedRect(layer->drawTransform(), updateContentRect);
         targetDamageRect.uniteIfNonZero(updateRectInTargetSpace);