Fix shadowing warning in json_parser on VS2015

base/json/json_parser.cc

Index: base/json/json_parser.cc
diff --git a/base/json/json_parser.cc b/base/json/json_parser.cc
index 6a25bc7b481a3e1ca28b5532ad07ce957b360380..d42b1a3d37e820f0ff3f1b6cfb00dde6e3be9fc8 100644
--- a/base/json/json_parser.cc
+++ b/base/json/json_parser.cc
@@ -428,7 +428,7 @@ bool JSONParser::EatComment() {
   if (next_char == '/') {
     // Single line comment, read to newline.
     while (CanConsume(1)) {
-      char next_char = *NextChar();
+      next_char = *NextChar();
       if (next_char == '\n' || next_char == '\r')
         return true;
     }