Add OVERRIDE to base/.

base/json/json_value_serializer.h

Index: base/json/json_value_serializer.h
diff --git a/base/json/json_value_serializer.h b/base/json/json_value_serializer.h
index 650008ec235aab6d356098b7c8c5bde0c1f7b224..82fd9639c1a2c586a1961bfc7c140af07ea32b72 100644
--- a/base/json/json_value_serializer.h
+++ b/base/json/json_value_serializer.h
@@ -39,7 +39,7 @@ class BASE_EXPORT JSONStringValueSerializer : public base::ValueSerializer {
   // Attempt to serialize the data structure represented by Value into
   // JSON.  If the return value is true, the result will have been written
   // into the string passed into the constructor.
-  virtual bool Serialize(const Value& root);
+  virtual bool Serialize(const Value& root) OVERRIDE;
 
   // Attempt to deserialize the data structure encoded in the string passed
   // in to the constructor into a structure of Value objects.  If the return
@@ -48,7 +48,8 @@ class BASE_EXPORT JSONStringValueSerializer : public base::ValueSerializer {
   // If |error_message| is non-null, it will be filled in with a formatted
   // error message including the location of the error if appropriate.
   // The caller takes ownership of the returned value.
-  virtual Value* Deserialize(int* error_code, std::string* error_message);
+  virtual Value* Deserialize(int* error_code,
+                             std::string* error_message) OVERRIDE;
 
   void set_pretty_print(bool new_value) { pretty_print_ = new_value; }
   bool pretty_print() { return pretty_print_; }
@@ -86,7 +87,7 @@ class BASE_EXPORT JSONFileValueSerializer : public base::ValueSerializer {
   // Attempt to serialize the data structure represented by Value into
   // JSON.  If the return value is true, the result will have been written
   // into the file whose name was passed into the constructor.
-  virtual bool Serialize(const Value& root);
+  virtual bool Serialize(const Value& root) OVERRIDE;
 
   // Attempt to deserialize the data structure encoded in the file passed
   // in to the constructor into a structure of Value objects.  If the return
@@ -95,7 +96,8 @@ class BASE_EXPORT JSONFileValueSerializer : public base::ValueSerializer {
   // If |error_message| is non-null, it will be filled in with a formatted
   // error message including the location of the error if appropriate.
   // The caller takes ownership of the returned value.
-  virtual Value* Deserialize(int* error_code, std::string* error_message);
+  virtual Value* Deserialize(int* error_code,
+                             std::string* error_message) OVERRIDE;
 
   // This enum is designed to safely overlap with JSONReader::JsonParseError.
   enum JsonFileError {