cc: don't add low-res tiling to GPU rasterized layers.

cc/layers/picture_layer_impl.cc

Index: cc/layers/picture_layer_impl.cc
diff --git a/cc/layers/picture_layer_impl.cc b/cc/layers/picture_layer_impl.cc
index 08b42c5f63a7d6d690033e9a99390f6810a7bf24..4f85e352b69d2684022980b506165770c581598e 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -945,8 +945,9 @@ void PictureLayerImpl::ManageTilings(bool animating_transform_to_screen) {
   // prevents wastefully creating a paired low res tiling for every new high res
   // tiling during a pinch or a CSS animation.
   bool is_pinching = layer_tree_impl()->PinchGestureActive();
-  if (!is_pinching && !animating_transform_to_screen && !low_res &&
-      low_res != high_res)
+  if (ShouldHaveLowResTiling() && !is_pinching &&

[vmpstr, 2014/01/10 00:52:02]

We could technically have a case where after a super quick pinch zoom, we get
that the previous high res contents scale is now a low res contents scale, which
would avoid this check but still have a low res tiling? I mean that's probably
highly unlikely...

Would setting low_res_factor to 1 in GPU raster case around line 1058 in this
file also get rid of the low res tiling?

[enne (OOO), 2014/01/10 01:42:34]

I don't think so.  I think you'd maybe need to add an additional case to
PictureLayerImpl::CleanUpTilingsOnActiveLayer to clean up low res tilings on
layers that shouldn't have low res tilings.  Or remove it here?

+      !animating_transform_to_screen &&
+      !low_res && low_res != high_res)
     low_res = AddTiling(low_res_raster_contents_scale_);
 
   // Set low-res if we have one.