Adds mailto: URL support to app launching.

ios/chrome/browser/web/mailto_handler_gmail_unittest.mm

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ios/chrome/browser/web/mailto_handler_gmail.h"
+
+#include "testing/gtest/include/gtest/gtest.h"
+#include "testing/gtest_mac.h"
+#include "url/gurl.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+TEST(MailtoHandlerGmailTest, TestConstructor) {
+  MailtoHandlerGmail* handler = [[MailtoHandlerGmail alloc] init];
+  EXPECT_NSEQ(@"Gmail", [handler appName]);
+  EXPECT_NSEQ(@"422689480", [handler appStoreID]);
+  EXPECT_NSEQ(@"googlegmail:/co?", [handler beginningScheme]);
+}