Adds mailto: URL support to app launching.

ios/chrome/app/strings/ios_strings.grd

Index: ios/chrome/app/strings/ios_strings.grd
diff --git a/ios/chrome/app/strings/ios_strings.grd b/ios/chrome/app/strings/ios_strings.grd
index 768248b8a1a152a14f792eaaa1010652b7974faa..a0c4646f6504d933670468355fa4a339a319e7af 100644
--- a/ios/chrome/app/strings/ios_strings.grd
+++ b/ios/chrome/app/strings/ios_strings.grd
@@ -1516,6 +1516,9 @@ Your data was encrypted with your sync passphrase on <ph name="TIME">$2<ex>Sept
       <message name="IDS_IOS_SIGNIN_PROMO_NOT" desc="Button that the user can press if they are not the profile that Chrome found (opposite of 'Continue as Joe Doe').">
         Not <ph name="EMAIL">$1<ex>john.doe@example.com</ex>?</ph>
       </message>
+      <message name="IDS_IOS_SYSTEM_MAIL_APP" desc="Name of iOS System-provided Mail app. Note that this is not consistently translated in al locales, e.g. it is still 'Mail' in French, but is translated to '邮件' in Chinese locale. [Length: 10em]">
+        Mail
+      </message>
     </messages>
   </release>
 </grit>