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

cc/resources/picture_layer_tiling.h

Index: cc/resources/picture_layer_tiling.h
diff --git a/cc/resources/picture_layer_tiling.h b/cc/resources/picture_layer_tiling.h
index 15fdb4320eea2c640107054bfef7298e423ce0fa..e6b935886056caefca0350d5a5dea8598b43cfa4 100644
--- a/cc/resources/picture_layer_tiling.h
+++ b/cc/resources/picture_layer_tiling.h
@@ -21,10 +21,17 @@
 #include "ui/gfx/geometry/rect.h"
 
 namespace base {
-namespace debug {
+namespace trace_event {
 class TracedValue;
 }
+
+// This is added temporarily. Once the renaming of namespace usages
+// accross all folders are done, this will be removed.
+// TODO(ssid): crrev.com/837303004
+namespace debug {
+using ::base::trace_event::TracedValue;
 }
+}  // namespace base
 
 namespace cc {