Keeping track of descendants that draw content instead of recalcualting

cc/layers/image_layer.cc

Index: cc/layers/image_layer.cc
diff --git a/cc/layers/image_layer.cc b/cc/layers/image_layer.cc
index cada84df3ccb4a0ce63731db532f2e0cd1f08358..c10b56546f21a2f0c1c584238c6be801bbbeae66 100644
--- a/cc/layers/image_layer.cc
+++ b/cc/layers/image_layer.cc
@@ -30,9 +30,14 @@ void ImageLayer::SetBitmap(const SkBitmap& bitmap) {
     return;
 
   bitmap_ = bitmap;
+  UpdateDrawsContent();
   SetNeedsDisplay();
 }
 
+bool ImageLayer::HasDrawableContent() const {
+  return !bitmap_.isNull() && TiledLayer::HasDrawableContent();

[danakj, 2014/07/14 20:22:02]

Ok this is more clear to me what's going on, but I guess I'm not excited about
this being separate from the places that call UpdateDrawsContent without it
being clear why we called UpdateDrawsContent where we did.

Before, I disliked the UpdateDrawsContent(true) call, but it had similar
properties of disconnecting this logic from the UpdateDrawsContent call.

I wish we didn't have to deal with multiple levels up inheritance here. But ok
one more suggestion that I think will help make this relationship more clear.
How about we pass the return value of HasDrawableContent() to
UpdateDrawsContent() instead of having it call back to that method.

Then the relation between these two methods is more obvious down in these
subclasses.

[awoloszyn, 2014/07/16 20:44:19]

Done.

+}
+
 void ImageLayer::SetTexturePriorities(const PriorityCalculator& priority_calc) {
   // Update the tile data before creating all the layer's tiles.
   UpdateTileSizeAndTilingOption();
@@ -77,10 +82,6 @@ void ImageLayer::CalculateContentsScale(float ideal_contents_scale,
   *content_bounds = gfx::Size(bitmap_.width(), bitmap_.height());
 }
 
-bool ImageLayer::DrawsContent() const {
-  return !bitmap_.isNull() && TiledLayer::DrawsContent();
-}
-
 void ImageLayer::OnOutputSurfaceCreated() {
   SetTextureFormat(
       layer_tree_host()->GetRendererCapabilities().best_texture_format);