cc: When the transform's scale is unknown, draw render surfaces at the resolution of the screen.

cc/layer_tree_host_common.cc

Index: cc/layer_tree_host_common.cc
diff --git a/cc/layer_tree_host_common.cc b/cc/layer_tree_host_common.cc
index b9fc38083f32150ab968b4c6e0e2770216c7a2be..bdd0aff1a04737ba8650c4464e775d0e3f87266b 100644
--- a/cc/layer_tree_host_common.cc
+++ b/cc/layer_tree_host_common.cc
@@ -390,7 +390,7 @@ static inline void updateLayerContentsScale(Layer* layer, const gfx::Transform&
         rasterScale = 1;
 
         if (!animatingTransformToScreen && layer->automaticallyComputeRasterScale()) {
-            gfx::Vector2dF transformScale = MathUtil::computeTransform2dScaleComponents(combinedTransform);
+            gfx::Vector2dF transformScale = MathUtil::computeTransform2dScaleComponents(combinedTransform, 1.f);

[enne (OOO), 2012/12/20 19:43:36]

This is 1, because the contents scaling layers will automatically take into
account the device scale?

[danakj, 2012/12/20 22:42:30]

This is 1 because we multiply by device scale factor and (sometimes) pagescale
factor down below on line 406.

It's choosing the "rasterScale" here, not the final "contentsScale"

[enne (OOO), 2012/12/20 23:18:48]

True.  If you pick 1, then rasterScale = 1 / DSF or 1 / (DSF*PSF) but you happen
to clamp to 1 before using it, meaning that contents scale = 1 * DSF (and maybe
* PSF).  I guess that works out, but it seems a little magical.

[danakj, 2012/12/20 23:20:57]

The reason we do it this way, and it's so different from the rendersurface case
which is much simpler is:

- This is main thread only.
- This computed value is saved permanently on the layer as the rasterScale.
- This value is then combined with the page and device scale factors in every
future iteration to form the current contentsScale.

Whereas the rendersurface one is both threads (but really affects impl) and is a
throwaway value, used only for the current frame.

             float combinedScale = std::max(transformScale.x(), transformScale.y());
             rasterScale = combinedScale / deviceScaleFactor;
             if (!layer->boundsContainPageScale())
@@ -660,7 +660,7 @@ static void calculateDrawPropertiesInternal(LayerType* layer, const gfx::Transfo
     gfx::Transform nextHierarchyMatrix = fullHierarchyMatrix;
     gfx::Transform sublayerMatrix;
 
-    gfx::Vector2dF renderSurfaceSublayerScale = MathUtil::computeTransform2dScaleComponents(combinedTransform);
+    gfx::Vector2dF renderSurfaceSublayerScale = MathUtil::computeTransform2dScaleComponents(combinedTransform, deviceScaleFactor * pageScaleFactor);
 
     if (subtreeShouldRenderToSeparateSurface(layer, combinedTransform.IsScaleOrTranslation())) {
         // Check back-face visibility before continuing with this surface and its subtree