cc: Report only on active tiles in tracing.

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index a6d50c6a50beb8ef63f40617ed62ce3bcb3d060a..e293a5aa9ad34723305fe31def6293258d0cad95 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -3145,11 +3145,25 @@ void LayerTreeHostImpl::AsValueWithFrameInto(
   state->BeginDictionary("device_viewport_size");
   MathUtil::AddToTracedValue(device_viewport_size_, state);
   state->EndDictionary();
-  if (tile_manager_) {
-    state->BeginArray("tiles");
-    tile_manager_->AllTilesAsValueInto(state);
-    state->EndArray();
 
+  std::set<const Tile*> tiles;
+  active_tree_->GetAllTilesForTracing(&tiles);
+  if (pending_tree_)
+    pending_tree_->GetAllTilesForTracing(&tiles);
+
+  state->BeginArray("active_tiles");
+  for (std::set<const Tile*>::const_iterator it = tiles.begin();
+       it != tiles.end();
+       ++it) {
+    const Tile* tile = *it;
+
+    state->BeginDictionary();
+    tile->AsValueInto(state);
+    state->EndDictionary();
+  }
+  state->EndArray();
+
+  if (tile_manager_) {
     state->BeginDictionary("tile_manager_basic_state");
     tile_manager_->BasicStateAsValueInto(state);
     state->EndDictionary();