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

cc/scheduler/scheduler_state_machine.h

Index: cc/scheduler/scheduler_state_machine.h
diff --git a/cc/scheduler/scheduler_state_machine.h b/cc/scheduler/scheduler_state_machine.h
index 5b7f6b78365d9a10b8631158e7c343edbb0cf006..fb87c84bf6488366b2780d96786af22b5780ae9b 100644
--- a/cc/scheduler/scheduler_state_machine.h
+++ b/cc/scheduler/scheduler_state_machine.h
@@ -17,12 +17,19 @@
 #include "cc/scheduler/scheduler_settings.h"
 
 namespace base {
-namespace debug {
+namespace trace_event {
 class ConvertableToTraceFormat;
 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::ConvertableToTraceFormat;
+using ::base::trace_event::TracedValue;
 }
+class Value;
+}  // namespace base
 
 namespace cc {