cc: Support on demand raster with ganesh

cc/resources/raster_worker_pool.cc

Index: cc/resources/raster_worker_pool.cc
diff --git a/cc/resources/raster_worker_pool.cc b/cc/resources/raster_worker_pool.cc
index 8f71b2e249328299b81ed287a7f190561899bb4b..53b084150ab32655354a5441e5becd93da6dafa0 100644
--- a/cc/resources/raster_worker_pool.cc
+++ b/cc/resources/raster_worker_pool.cc
@@ -46,15 +46,14 @@ class RasterTaskGraphRunner : public TaskGraphRunner,
 #endif
       workers_.push_back(worker.Pass());
     }
-
-    // Use index 0 for origin thread.
-    current_tls_.Set(new ThreadLocalState(0));
   }
 
   virtual ~RasterTaskGraphRunner() { NOTREACHED(); }
 
   size_t GetPictureCloneIndexForCurrentThread() {
-    return current_tls_.Get()->picture_clone_index;
+    // Use index 0 for origin thread and any unknown threads.

[reveman, 2014/06/20 18:44:19]

nit: "Use index 0 if called on non-raster thread."

+    ThreadLocalState* thread_local_state = current_tls_.Get();
+    return thread_local_state ? current_tls_.Get()->picture_clone_index : 0;
   }
 
  private: