Add URL generator / json parser for getting start_page_token of changes.

google_apis/drive/drive_api_parser.h

Index: google_apis/drive/drive_api_parser.h
diff --git a/google_apis/drive/drive_api_parser.h b/google_apis/drive/drive_api_parser.h
index 477ccfb4f7fbd1aa8a6ecaeba835008af852d2c4..60b586c659bd9b980897fcc382984f4240ab659a 100644
--- a/google_apis/drive/drive_api_parser.h
+++ b/google_apis/drive/drive_api_parser.h
@@ -964,6 +964,44 @@ class ChangeList {
   DISALLOW_COPY_AND_ASSIGN(ChangeList);
 };
 
+// StartPageToken is the starting pageToken for listing future changes.
+// https://developers.google.com/drive/v2/reference/changes/getStartPageToken
+class StartPageToken {
+ public:
+  StartPageToken();
+  ~StartPageToken();
+
+  // Registers the mapping between JSON field names and the members in this
+  // class.
+  static void RegisterJSONConverter(
+      base::JSONValueConverter<StartPageToken>* converter);
+
+  // Returns true if the |value| has kind field for StartPageToken.
+  static bool HasStartPageTokenKind(const base::Value& value);
+
+  // Creates an instance from parsed JSON.
+  static std::unique_ptr<StartPageToken> CreateFrom(const base::Value& value);
+
+  // Returns the starting page token for listing future changes.
+  const std::string& start_page_token() const { return start_page_token_; }
+
+  void set_start_page_token(const std::string& start_page_token) {
+    start_page_token_ = start_page_token;
+  }
+
+ private:
+  friend class DriveAPIParserTest;
+  FRIEND_TEST_ALL_PREFIXES(DriveAPIParserTest, StartPageTokenParser);
+
+  // Parses and initializes data members from content of |value|.
+  // Return false if parsing fails.
+  bool Parse(const base::Value& value);
+
+  std::string start_page_token_;
+
+  DISALLOW_COPY_AND_ASSIGN(StartPageToken);
+};
+
 }  // namespace google_apis
 
 #endif  // GOOGLE_APIS_DRIVE_DRIVE_API_PARSER_H_