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

google_apis/drive/drive_api_parser_unittest.cc

Index: google_apis/drive/drive_api_parser_unittest.cc
diff --git a/google_apis/drive/drive_api_parser_unittest.cc b/google_apis/drive/drive_api_parser_unittest.cc
index 443b692dbd978bc2d896b0140c515e790553be2c..fffd9f13605a442bbe653ed90d3239b614bc4ee9 100644
--- a/google_apis/drive/drive_api_parser_unittest.cc
+++ b/google_apis/drive/drive_api_parser_unittest.cc
@@ -250,6 +250,20 @@ TEST(DriveAPIParserTest, FileListParser) {
   EXPECT_EQ(0U, file3.open_with_links().size());
 }
 
+// Test start page token parsing.
+TEST(DriveAPIParserTest, StartPageTokenParser) {
+  std::string error;
+  std::unique_ptr<base::Value> document =
+      test_util::LoadJSONFile("drive/changes_start_page_token.json");
+  ASSERT_TRUE(document.get());
+  ASSERT_EQ(base::Value::Type::DICTIONARY, document->GetType());
+
+  std::unique_ptr<StartPageToken> start_page_token(new StartPageToken);
+  EXPECT_TRUE(start_page_token->Parse(*document));
+
+  EXPECT_EQ("TheStartPageToken", start_page_token->start_page_token());
+}
+
 // Test change list parsing.
 TEST(DriveAPIParserTest, ChangeListParser) {
   std::string error;