Update from https://crrev.com/315085

cc/layers/layer_client.h

Index: cc/layers/layer_client.h
diff --git a/cc/layers/layer_client.h b/cc/layers/layer_client.h
index 4b98a959dcac4c35fea2aaaf614a0724045c75cd..efdbe5105a11916268f72b3bc91870463ebb4038 100644
--- a/cc/layers/layer_client.h
+++ b/cc/layers/layer_client.h
@@ -11,10 +11,16 @@
 #include "cc/base/cc_export.h"
 
 namespace base {
-namespace debug {
+namespace trace_event {
 class ConvertableToTraceFormat;
 }
+
+// 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;
 }
+}  // namespace base
 
 namespace cc {