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

cc/quads/render_pass.h

Index: cc/quads/render_pass.h
diff --git a/cc/quads/render_pass.h b/cc/quads/render_pass.h
index 8a40f1792514dbe14aea0f73f12fbe9425137ebf..28775883e5bc8085590dd273fe426e7538962714 100644
--- a/cc/quads/render_pass.h
+++ b/cc/quads/render_pass.h
@@ -20,17 +20,11 @@
 #include "ui/gfx/transform.h"
 
 namespace base {
-namespace trace_event {
+namespace debug {
 class TracedValue;
 }
 class Value;
-
-// 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::TracedValue;
-}
-}  // namespace base
+};
 
 namespace cc {