Makes tile-creation lazy

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 fd4a85ae1caa3b84baf979acd5d26efc89d90fb5..cb986fef900ab06e5d933c08a28d81c67566b888 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -81,7 +81,6 @@ void PictureLayerImpl::PushPropertiesTo(LayerImpl* base_layer) {
   layer_impl->raster_source_scale_ = raster_source_scale_;
 }
 
-
 void PictureLayerImpl::AppendQuads(QuadSink* quadSink,
                                    AppendQuadsData* appendQuadsData) {
   const gfx::Rect& rect = visible_content_rect();
@@ -320,7 +319,8 @@ skia::RefPtr<SkPicture> PictureLayerImpl::GetPicture() {
 }
 
 scoped_refptr<Tile> PictureLayerImpl::CreateTile(PictureLayerTiling* tiling,
-                                                 gfx::Rect content_rect) {
+                                                 const gfx::Rect& content_rect,

[enne (OOO), 2013/03/27 16:16:27]

No.  Please stay consistent with passing rect by value in the rest of cc.  If
you want to change this policy, make some measurements and put up a separate
patch that changes it everywhere.  Don't just change it in this one place.

Localized churn based on differing personal opinion is not how we do things.

[whunt, 2013/03/27 17:42:02]

I'll switch it back but the policy needs to be changed:
https://docs.google.com/a/google.com/document/d/1LMBDUB64tR5ji3FkHYJCYJb3cgCz...

[enne (OOO), 2013/03/27 18:03:20]

I'm aware of your doc.  This is outside the scope of this code review, but if
you want to change this behavior, make some measurements to demonstrate that
this has a performance impact and is worth changing, and I'll be convinced
enough to lgtⅿ changing it everywhere.

+                                                 const gfx::Rect& paint_rect) {
   if (!pile_->CanRaster(tiling->contents_scale(), content_rect))
     return scoped_refptr<Tile>();
 
@@ -330,6 +330,7 @@ scoped_refptr<Tile> PictureLayerImpl::CreateTile(PictureLayerTiling* tiling,
       content_rect.size(),
       GL_RGBA,
       content_rect,
+      paint_rect,
       contents_opaque() ? content_rect : gfx::Rect(),
       tiling->contents_scale(),
       id()));
@@ -339,6 +340,24 @@ void PictureLayerImpl::UpdatePile(Tile* tile) {
   tile->set_picture_pile(pile_);
 }
 
+const Region* PictureLayerImpl::GetInvalidation() {
+  return &invalidation_;
+}
+
+const PictureLayerTiling* PictureLayerImpl::GetSibling(
+    const PictureLayerTiling* tiling) {
+
+  const PictureLayerImpl* other_layer = layer_tree_impl()->IsActiveTree() ?
+      PendingTwin() : ActiveTwin();
+  if (!other_layer)
+    return NULL;
+  for (size_t i = 0; i < other_layer->tilings_->num_tilings(); ++i)
+    if (other_layer->tilings_->tiling_at(i)->contents_scale() ==
+        tiling->contents_scale())
+      return other_layer->tilings_->tiling_at(i);
+  return NULL;
+}
+
 gfx::Size PictureLayerImpl::CalculateTileSize(
     gfx::Size current_tile_size,
     gfx::Size content_bounds) {