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

R=enne@chromium.org,vmpstr@chromium.org
BUG=332593

Review URL: https://codereview.chromium.org/132083007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244227 0039d316-1c4b-4281-b951-d872f2087c98

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 &&
+      !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.
@@ -1092,8 +1093,8 @@ void PictureLayerImpl::CleanUpTilingsOnActiveLayer(
         tiling->contents_scale() <= max_acceptable_high_res_scale)
       continue;
 
-    // Low resolution can't activate, so only keep one around.
-    if (tiling->resolution() == LOW_RESOLUTION)
+    // Keep low resolution tilings, if the layer should have them.
+    if (tiling->resolution() == LOW_RESOLUTION && ShouldHaveLowResTiling())
       continue;
 
     // Don't remove tilings that are being used (and thus would cause a flash.)

cc/layers/picture_layer_impl.h

@@ -86,6 +86,9 @@ class CC_EXPORT PictureLayerImpl
   void RemoveAllTilings();
   void SyncFromActiveLayer(const PictureLayerImpl* other);
   void ManageTilings(bool animating_transform_to_screen);
+  bool ShouldHaveLowResTiling() const {
+    return !should_use_gpu_rasterization();
+  }
   virtual bool ShouldAdjustRasterScale(
       bool animating_transform_to_screen) const;
   virtual void RecalculateRasterScales(

cc/layers/picture_layer_impl_unittest.cc

@@ -1430,7 +1430,7 @@ TEST_F(PictureLayerImplTest, TileSizeForGpuRasterization) {
 
   pending_layer_->CalculateContentsScale(
       1.f, 1.f, 1.f, false, &result_scale_x, &result_scale_y, &result_bounds);
-  ASSERT_EQ(2u, pending_layer_->tilings()->num_tilings());
+  ASSERT_EQ(1u, pending_layer_->tilings()->num_tilings());
 
   pending_layer_->tilings()->tiling_at(0)->CreateAllTilesForTesting();