[ios] Fix settings switch accessibility value and hint

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 deb1a90e6a8733c7785d18160f4168c72bc0ee5c..79f0ea2f6cc7ec12783d04c464de6e54dd4fb058 100644
--- a/ios/chrome/app/strings/ios_strings.grd
+++ b/ios/chrome/app/strings/ios_strings.grd
@@ -1197,6 +1197,9 @@ Handoff must also be enabled in the General section of Settings, and your device
       <message name="IDS_IOS_SETTING_ON" desc="Generic status label displayed in Settings to show that a setting is currently turned on. [Length: 5em] [iOS only]">
         On
       </message>
+      <message name="IDS_IOS_TOGGLE_SETTING_SWITCH_ACCESSIBILITY_HINT" desc="Action hint for any switch in settings. This is spoken by VoiceOver. [iOS only]">
+        Double tap to toggle setting

[edchin, 2017/01/12 22:13:45]

The guidelines suggest not to mention 'tap': "Don’t repeat the action type in
the hint. For example, do not create hints such as “Tap to play the song” or
“Tapping plays the song.”
https://developer.apple.com/reference/objectivec/nsobject/1615093-accessibili...

[sczs, 2017/01/12 22:26:17]

I think the difference is that this is a switch, so its not something that you
would tap intuitively. On the other hand no action type is being repeated, Voice
Over will read: "Cell Text, ON/OFF.... Double tap to toggle setting" which is
the exact same hint that iOS switch settings use. 

[edchin, 2017/01/12 22:37:54]

Acknowledged.

[lpromero, 2017/01/13 10:01:33]

No action needed: I wanted to follow Apple's example in the Settings app, where
they use "Double tap to toggle setting". Note that they don't add the Button
trait to the cell, so it might be less redundant.

+      </message>
       <message name="IDS_IOS_SHARE_EMAIL_COMPLETE" desc="Message shown when email share has been sent. [Length: Unknown. Keep it short.] [iOS only]">
         Mail sent.
       </message>