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 606d3d901a658eb4090ded867d9aeec3fa480bb4..b271098cdd28e3a5063609505468fcaacb80bc42 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -90,7 +90,6 @@ void PictureLayerImpl::PushPropertiesTo(LayerImpl* base_layer) {
   layer_impl->is_using_lcd_text_ = is_using_lcd_text_;
 }
 
-
 void PictureLayerImpl::AppendQuads(QuadSink* quad_sink,
                                    AppendQuadsData* append_quads_data) {
   const gfx::Rect& rect = visible_content_rect();
@@ -372,6 +371,24 @@ void PictureLayerImpl::UpdatePile(Tile* tile) {
   tile->set_picture_pile(pile_);
 }
 
+const Region* PictureLayerImpl::GetInvalidation() {
+  return &invalidation_;
+}
+
+const PictureLayerTiling* PictureLayerImpl::GetTwinTiling(
+    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) {
@@ -464,31 +481,20 @@ void PictureLayerImpl::SyncFromActiveLayer(const PictureLayerImpl* other) {
     }
   }
 
-  tilings_->CloneAll(*other->tilings_, invalidation_, MinimumContentsScale());
-  DCHECK(bounds() == tilings_->LayerBounds());
+  // Union in the other newly exposed regions as invalid.
+  Region difference_region = Region(gfx::Rect(bounds()));
+  difference_region.Subtract(gfx::Rect(other->bounds()));
+  invalidation_.Union(difference_region);
 
-  // It's a sad but unfortunate fact that PicturePile tiling edges do not line
-  // up with PictureLayerTiling edges.  Tiles can only be added if they are
-  // entirely covered by recordings (that may come from multiple PicturePile
-  // tiles).  This check happens in this class's CreateTile() call.
-  for (int x = 0; x < pile_->num_tiles_x(); ++x) {
-    for (int y = 0; y < pile_->num_tiles_y(); ++y) {
-      bool previously_had = other->pile_->HasRecordingAt(x, y);
-      bool now_has = pile_->HasRecordingAt(x, y);
-      if (!now_has || previously_had)
-        continue;
-      gfx::Rect layer_rect = pile_->tile_bounds(x, y);
-      tilings_->CreateTilesFromLayerRect(layer_rect);
-    }
-  }
+  tilings_->CloneAll(*other->tilings_, MinimumContentsScale());
+  DCHECK(bounds() == tilings_->LayerBounds());
 }
 
 void PictureLayerImpl::SyncTiling(
-    const PictureLayerTiling* tiling,
-    const Region& pending_layer_invalidation) {
+    const PictureLayerTiling* tiling) {
   if (!DrawsContent() || tiling->contents_scale() < MinimumContentsScale())
     return;
-  tilings_->Clone(tiling, pending_layer_invalidation);
+  tilings_->Clone(tiling);
 }
 
 void PictureLayerImpl::SetIsMask(bool is_mask) {
@@ -571,18 +577,15 @@ PictureLayerTiling* PictureLayerImpl::AddTiling(float contents_scale) {
   const Region& recorded = pile_->recorded_region();
   DCHECK(!recorded.IsEmpty());
 
-  for (Region::Iterator iter(recorded); iter.has_rect(); iter.next())
-    tiling->CreateTilesFromLayerRect(iter.rect());
-
   PictureLayerImpl* twin =
       layer_tree_impl()->IsPendingTree() ? ActiveTwin() : PendingTwin();
   if (!twin)
     return tiling;
 
   if (layer_tree_impl()->IsPendingTree())

[enne (OOO), 2013/03/29 20:50:58]

This if statement can be simplified.

[whunt, 2013/03/29 21:52:04]

Clearly. I'll go do that.

-    twin->SyncTiling(tiling, invalidation_);
+    twin->SyncTiling(tiling);
   else
-    twin->SyncTiling(tiling, twin->invalidation_);
+    twin->SyncTiling(tiling);
 
   return tiling;
 }
@@ -848,10 +851,6 @@ void PictureLayerImpl::UpdateLCDTextStatus() {
   pending_layer->is_using_lcd_text_ = is_using_lcd_text_;
   pending_layer->pile_ = PicturePileImpl::CreateFromOther(pending_layer->pile_,
                                                           is_using_lcd_text_);
-
-  // TODO(enne): if we tracked text regions, we could just invalidate those
-  // directly rather than tossing away every tile.
-  pending_layer->tilings_->Invalidate(gfx::Rect(bounds()));

[enne (OOO), 2013/03/29 20:50:58]

This is incorrect to remove wholesale.  Invalidate both deletes and creates new
tiles.  Your patch defers creation, but I think you still need to somehow do the
deletion here because there now a bunch of tiles that need to be rerastered.

[whunt, 2013/03/29 21:52:04]

Good call, I'll investigate the best way to keep the correct behavior.

[whunt, 2013/03/29 22:17:55]

On second thought, I'm not actually sure, we should discuss.

 }
 
 void PictureLayerImpl::GetDebugBorderProperties(