Update from https://crrev.com/329939

base/trace_event/trace_event_argument.h

Index: base/trace_event/trace_event_argument.h
diff --git a/base/trace_event/trace_event_argument.h b/base/trace_event/trace_event_argument.h
index 78d37d4122947ce9eecccc7afc016eeafa9aceff..d86cfd1f82aecbb126688c83874f211dc0d16360 100644
--- a/base/trace_event/trace_event_argument.h
+++ b/base/trace_event/trace_event_argument.h
@@ -29,7 +29,7 @@ class BASE_EXPORT TracedValue : public ConvertableToTraceFormat {
   void SetDouble(const char* name, double);
   void SetBoolean(const char* name, bool value);
   void SetString(const char* name, const std::string& value);
-  void SetValue(const char* name, Value* value);
+  void SetValue(const char* name, scoped_ptr<Value> value);
   void BeginDictionary(const char* name);
   void BeginArray(const char* name);
 
@@ -49,7 +49,7 @@ class BASE_EXPORT TracedValue : public ConvertableToTraceFormat {
   ListValue* GetCurrentArray();
 
   scoped_ptr<base::Value> root_;
-  std::vector<Value*> stack_;
+  std::vector<Value*> stack_;  // Weak references.
   DISALLOW_COPY_AND_ASSIGN(TracedValue);
 };