Fix potential NULL pointer in LayerTreeHostImpl

cc/trees/layer_tree_host_impl.cc

 // Copyright 2011 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/trees/layer_tree_host_impl.h"
 
 #include <algorithm>
 
 #include "base/basictypes.h"
 #include "base/json/json_writer.h"
@@ skipping 2184 matching lines @@
              MathUtil::AsValue(device_viewport_size_).release());
   if (tile_manager_)
     state->Set("tiles", tile_manager_->AllTilesAsValue().release());
   state->Set("active_tree", active_tree_->AsValue().release());
   if (pending_tree_)
     state->Set("pending_tree", pending_tree_->AsValue().release());
   return state.PassAs<base::Value>();
 }
 
 scoped_ptr<base::Value> LayerTreeHostImpl::ActivationStateAsValue() const {
-  DCHECK(pending_tree_ && tile_manager_);
   scoped_ptr<base::DictionaryValue> state(new base::DictionaryValue());
   state->Set("lthi", TracedValue::CreateIDRef(this).release());
-  state->Set("tile_manager", tile_manager_->BasicStateAsValue().release());
+  if (tile_manager_)
+    state->Set("tile_manager", tile_manager_->BasicStateAsValue().release());
   return state.PassAs<base::Value>();
 }
 
 // static
 LayerImpl* LayerTreeHostImpl::GetNonCompositedContentLayerRecursive(
     LayerImpl* layer) {
   if (!layer)
     return NULL;
 
   if (layer->DrawsContent())
@@ skipping 17 matching lines @@
 }
 
 void LayerTreeHostImpl::SetDebugState(const LayerTreeDebugState& debug_state) {
   if (debug_state_.continuous_painting != debug_state.continuous_painting)
     paint_time_counter_->ClearHistory();
 
   debug_state_ = debug_state;
 }
 
 }  // namespace cc