Adds mailto: URL support to app launching.

ios/chrome/browser/web/external_app_launcher.mm

 // Copyright 2012 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.
 
 #import "ios/chrome/browser/web/external_app_launcher.h"
 
 #include "base/ios/ios_util.h"
 #include "base/logging.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/sys_string_conversions.h"
 #include "components/strings/grit/components_strings.h"
 #include "ios/chrome/browser/experimental_flags.h"
 #import "ios/chrome/browser/open_url_util.h"
+#import "ios/chrome/browser/web/mailto_url_rewriter.h"
 #include "ios/chrome/grit/ios_strings.h"
 #import "net/base/mac/url_conversions.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "url/gurl.h"
+#include "url/url_constants.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 namespace {
 
 typedef void (^AlertHandler)(UIAlertAction* action);
 
 // Returns a set of NSStrings that are URL schemes for iTunes Stores.
@@ skipping 17 matching lines @@
 }
 
 // Logs an entry for |Tab.ExternalApplicationOpened|.  If the user decided to
 // open in an external app, pass true.  Otherwise, if the user cancelled the
 // opening, pass false.
 void RecordExternalApplicationOpened(bool opened) {
   UMA_HISTOGRAM_BOOLEAN("Tab.ExternalApplicationOpened", opened);
 }
 
 // Returns whether gURL has the scheme of a URL that initiates a call.
-BOOL UrlHasPhoneCallScheme(const GURL& gURL) {
+bool UrlHasPhoneCallScheme(const GURL& gURL) {
   return gURL.SchemeIs("tel") || gURL.SchemeIs("facetime") ||
          gURL.SchemeIs("facetime-audio");
 }
 
 // Returns a string to be used as the label for the prompt's action button.
 NSString* PromptActionString(NSString* scheme) {
   if ([scheme isEqualToString:@"facetime"])
     return l10n_util::GetNSString(IDS_IOS_FACETIME_BUTTON);
   else if ([scheme isEqualToString:@"tel"] ||
            [scheme isEqualToString:@"facetime-audio"])
@@ skipping 113 matching lines @@
     // Prompt user to open itunes when opening it is not a result of a link
     // click.
     if (!linkClicked && UrlHasAppStoreScheme(gURL)) {
       [self performSelector:@selector(openExternalAppWithPromptForURL:)
                  withObject:URL
                  afterDelay:0.0];
       return YES;
     }
   }
 
+  // Replaces |URL| with a rewritten URL if it is of mailto: scheme.
+  if (!experimental_flags::IsNativeAppLauncherEnabled() &&
+      gURL.SchemeIs(url::kMailToScheme)) {
+    MailtoURLRewriter* rewriter =
+        [[MailtoURLRewriter alloc] initWithStandardHandlers];
+    NSString* launchURL = [rewriter rewriteMailtoURL:gURL];
+    if (launchURL) {
+      UMA_HISTOGRAM_BOOLEAN("MailtoURLRewriter.Rewritten", true);
+      URL = [NSURL URLWithString:launchURL];
+    } else {
+      UMA_HISTOGRAM_BOOLEAN("MailtoURLRewriter.Rewritten", false);

[Alexei Svitkine (slow), 2017/05/08 14:56:01]

Each UMA macro expands to a bunch of code. Please move this logging to below the
if in a single macro and pass in launchURL != nil

[pkl (ping after 24h if needed), 2017/05/08 17:07:56]

Great point! I was thinking of the number of times launchURL is tested, not from
the macro expansion. Fixed now.

+    }
+  }
+
   // If the following call returns YES, an external application is about to be
   // launched and Chrome will go into the background now.
   // TODO(crbug.com/622735): This call still needs to be updated.
   // It's heavily nested so some refactoring is needed.
   return [[UIApplication sharedApplication] openURL:URL];
 }
 
 @end