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

cc/resources/tile_manager.h

Index: cc/resources/tile_manager.h
diff --git a/cc/resources/tile_manager.h b/cc/resources/tile_manager.h
index 37ab765b84a8d904c7a2f89ce8dce50f9d02658d..0af823ed9c24fb309d49f77b8f1d33eb8c864a73 100644
--- a/cc/resources/tile_manager.h
+++ b/cc/resources/tile_manager.h
@@ -26,11 +26,18 @@
 #include "cc/resources/tile_task_runner.h"
 
 namespace base {
-namespace debug {
+namespace trace_event {
 class ConvertableToTraceFormat;
 class TracedValue;
 }
+
+// TODO(ssid): remove these aliases after the tracing clients are moved to the
+// new trace_event namespace. See crbug.com/451032. ETA: March 2015
+namespace debug {
+using ::base::trace_event::ConvertableToTraceFormat;
+using ::base::trace_event::TracedValue;
 }
+}  // namespace base
 
 namespace cc {
 class PictureLayerImpl;