Revert 277964 "cc: In SyncFromActiveLayer, drop all tiles not in..."

trunk/src/cc/layers/picture_layer_impl.cc

Index: trunk/src/cc/layers/picture_layer_impl.cc
===================================================================
--- trunk/src/cc/layers/picture_layer_impl.cc	(revision 277979)
+++ trunk/src/cc/layers/picture_layer_impl.cc	(working copy)
@@ -626,7 +626,6 @@
 }
 
 void PictureLayerImpl::SyncFromActiveLayer(const PictureLayerImpl* other) {
-  TRACE_EVENT0("cc", "SyncFromActiveLayer");
   DCHECK(!other->needs_post_commit_initialization_);
   DCHECK(other->tilings_);
 
@@ -641,6 +640,23 @@
   raster_contents_scale_ = other->raster_contents_scale_;
   low_res_raster_contents_scale_ = other->low_res_raster_contents_scale_;
 
+  // Add synthetic invalidations for any recordings that were dropped.  As
+  // tiles are updated to point to this new pile, this will force the dropping
+  // of tiles that can no longer be rastered.  This is not ideal, but is a
+  // trade-off for memory (use the same pile as much as possible, by switching
+  // during DidBecomeActive) and for time (don't bother checking every tile
+  // during activation to see if the new pile can still raster it).
+  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);
+      invalidation_.Union(layer_rect);
+    }
+  }
+
   // Union in the other newly exposed regions as invalid.
   Region difference_region = Region(gfx::Rect(bounds()));
   difference_region.Subtract(gfx::Rect(other->bounds()));