Update JSONReader to take base::StringPiece instead of std::string

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 b1edfb07edd4c2bd7c736cb150e24e77703deab0..daa20c5575cc19c660be79f98f1c09b9a2ecf406 100644
--- a/base/json/json_reader.h
+++ b/base/json/json_reader.h
@@ -33,6 +33,7 @@
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
+#include "base/string_piece.h"
 
 // Chromium and Chromium OS check out gtest to different places, so we're
 // unable to compile on both if we include gtest_prod.h here.  Instead, include
@@ -121,13 +122,13 @@ class BASE_EXPORT JSONReader {
   // instance. If |json| is not a properly formed JSON string, returns NULL.
   // If |allow_trailing_comma| is true, we will ignore trailing commas in
   // objects and arrays even though this goes against the RFC.
-  static Value* Read(const std::string& json, bool allow_trailing_comma);
+  static Value* Read(const StringPiece& json, bool allow_trailing_comma);
 
   // Reads and parses |json| like Read(). |error_code_out| and |error_msg_out|
   // are optional. If specified and NULL is returned, they will be populated
   // an error code and a formatted error message (including error location if
   // appropriate). Otherwise, they will be unmodified.
-  static Value* ReadAndReturnError(const std::string& json,
+  static Value* ReadAndReturnError(const StringPiece& json,
                                    bool allow_trailing_comma,
                                    int* error_code_out,
                                    std::string* error_msg_out);
@@ -151,7 +152,7 @@ class BASE_EXPORT JSONReader {
   // array. Otherwise, it can be any valid JSON type.
   // If |allow_trailing_comma| is true, we will ignore trailing commas in
   // objects and arrays even though this goes against the RFC.
-  Value* JsonToValue(const std::string& json, bool check_root,
+  Value* JsonToValue(const StringPiece& json, bool check_root,
                      bool allow_trailing_comma);
 
  private: