Reland Allow one-copy and zero-copy task tile worker pools to use compressed textures.

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 93d9bf1473bfffc9c792aca41021151615b22b96..695f539b5ea62f944a4ffe35bec48a899b06749b 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -52,6 +52,10 @@ const int kMinHeightForGpuRasteredTile = 256;
 // of using the same tile size.
 const int kTileRoundUp = 64;
 
+// For performance reasons and to support compressed tile textures, tile
+// width and height should be an even multiple of 4 in size.
+const int kTileMinimalAlignment = 4;
+
 }  // namespace
 
 namespace cc {
@@ -781,6 +785,10 @@ gfx::Size PictureLayerImpl::CalculateTileSize(
     tile_height = std::min(tile_height, default_tile_height);
   }
 
+  // Ensure that tile width and height are properly aligned.
+  tile_width = MathUtil::UncheckedRoundUp(tile_width, kTileMinimalAlignment);
+  tile_height = MathUtil::UncheckedRoundUp(tile_height, kTileMinimalAlignment);
+
   // Under no circumstance should we be larger than the max texture size.
   tile_width = std::min(tile_width, max_texture_size);
   tile_height = std::min(tile_height, max_texture_size);