cc: Add some more infrastructure for two trees

cc/picture_layer_impl.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/picture_layer_impl.h"
 
 #include "base/time.h"
 #include "cc/append_quads_data.h"
 #include "cc/checkerboard_draw_quad.h"
 #include "cc/debug_border_draw_quad.h"
@@ skipping 111 matching lines @@
     quadSink.append(quad.PassAs<DrawQuad>(), appendQuadsData);
   }
 }
 
 void PictureLayerImpl::dumpLayerProperties(std::string*, int indent) const {
   // TODO(enne): implement me
 }
 
 void PictureLayerImpl::didUpdateTransforms() {
   if (drawsContent()) {
-    // TODO(enne): Add more tilings during pinch zoom.
+    // TODO(enne): Add tilings during pinch zoom
+    // TODO(enne): Consider culling old tilings after pinch finishes.
     if (!tilings_.num_tilings()) {
       gfx::Size tile_size = layerTreeImpl()->settings().defaultTileSize;
-      tilings_.AddTiling(contentsScaleX(), tile_size);
-      // TODO(enne): handle invalidations, create new tiles
+      AddTiling(contentsScaleX(), tile_size);
+      // TODO(enne): Add a low-res tiling as well.
     }
   } else {
+    // TODO(enne): This should be unnecessary once there are two trees.
     tilings_.Reset();
   }
 
   gfx::Transform  current_screen_space_transform = screenSpaceTransform();
   double current_time =
       (base::TimeTicks::Now() - base::TimeTicks()).InSecondsF();
   double time_delta = 0;
   if (last_update_time_ != 0 && last_bounds_ == bounds() &&
       last_content_bounds_ == contentBounds() &&
       last_content_scale_x_ == contentsScaleX() &&
@@ skipping 26 matching lines @@
   return make_scoped_refptr(new Tile(
       tile_manager,
       pile_.get(),
       rect.size(),
       GL_RGBA,
       rect,
       tiling->contents_scale()));
 }
 
 void PictureLayerImpl::SyncFromActiveLayer(const PictureLayerImpl* other) {
-  tilings_.CloneFrom(other->tilings_);
+  tilings_.CloneAll(other->tilings_, invalidation_);
+}
+
+void PictureLayerImpl::SyncTilingFromActiveLayer(
+    const PictureLayerTiling* tiling) {
+  tilings_.Clone(tiling, invalidation_);
+}
+
+void PictureLayerImpl::AddTiling(float contents_scale, gfx::Size tile_size) {
+  const PictureLayerTiling* tiling = tilings_.AddTiling(
+      contents_scale,
+      tile_size);
+
+  // If a new tiling is created on the active tree, sync it to the pending tree
+  // so that it can share the same tiles.
+  if (layerTreeImpl()->IsActiveTree())
+    return;
+
+  PictureLayerImpl* pending_twin = static_cast<PictureLayerImpl*>(
+      layerTreeImpl()->PendingTreeLayerById(id()));
+  if (!pending_twin)
+    return;
+  DCHECK_EQ(id(), pending_twin->id());
+  pending_twin->SyncTilingFromActiveLayer(tiling);
 }
 
 }  // namespace cc