Cleanup: Better constify some strings in base.

base/json/json_reader.h

Index: base/json/json_reader.h
diff --git a/base/json/json_reader.h b/base/json/json_reader.h
index 79129cea9d1beab53b47f08d04059cb9b8b72cff..fd053d4336bf12ad2d812e7f0cbd3fd5b2acd881 100644
--- a/base/json/json_reader.h
+++ b/base/json/json_reader.h
@@ -75,14 +75,14 @@ class BASE_EXPORT JSONReader {
   };
 
   // String versions of parse error codes.
-  static const char* kInvalidEscape;
-  static const char* kSyntaxError;
-  static const char* kUnexpectedToken;
-  static const char* kTrailingComma;
-  static const char* kTooMuchNesting;
-  static const char* kUnexpectedDataAfterRoot;
-  static const char* kUnsupportedEncoding;
-  static const char* kUnquotedDictionaryKey;
+  static const char kInvalidEscape[];
+  static const char kSyntaxError[];
+  static const char kUnexpectedToken[];
+  static const char kTrailingComma[];
+  static const char kTooMuchNesting[];
+  static const char kUnexpectedDataAfterRoot[];
+  static const char kUnsupportedEncoding[];
+  static const char kUnquotedDictionaryKey[];
 
   // Constructs a reader with the default options, JSON_PARSE_RFC.
   JSONReader();