Move tracing namespace from base::debug to base::trace_event.

cc/resources/bitmap_tile_task_worker_pool.h

Index: cc/resources/bitmap_tile_task_worker_pool.h
diff --git a/cc/resources/bitmap_tile_task_worker_pool.h b/cc/resources/bitmap_tile_task_worker_pool.h
index 404a3a5f400f5e150060213778b3d6060624b367..b6c19f87372b9e220537e4cee9d6333b710a975b 100644
--- a/cc/resources/bitmap_tile_task_worker_pool.h
+++ b/cc/resources/bitmap_tile_task_worker_pool.h
@@ -11,9 +11,12 @@
 #include "cc/resources/tile_task_worker_pool.h"
 
 namespace base {
-namespace debug {
+namespace trace_event {
 class ConvertableToTraceFormat;
 }
+namespace debug {
+using ::base::trace_event::ConvertableToTraceFormat;
+}
 }
 
 namespace cc {