Adds mailto: URL support to app launching.

ios/chrome/browser/web/mailto_handler_system_mail_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_system_mail.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(MailtoHandlerSystemMailTest, TestConstructor) {
+  MailtoHandler* handler = [[MailtoHandlerSystemMail alloc] init];
+  EXPECT_TRUE(handler);
+  EXPECT_NSEQ(@"Mail", [handler appName]);
+  EXPECT_GT([[handler appStoreID] length], 0U);
+  EXPECT_TRUE([handler isAvailable]);
+}
+
+TEST(MailtoHandlerSystemMailTest, TestRewrite) {
+  MailtoHandler* handler = [[MailtoHandlerSystemMail alloc] init];
+  NSString* result = [handler rewriteMailtoURL:GURL("mailto:user@domain.com")];
+  EXPECT_NSEQ(@"mailto:user@domain.com", result);
+  result = [handler rewriteMailtoURL:GURL("http://www.google.com")];
+  EXPECT_FALSE(result);
+}