Disable auto-zoom on mobile form UIs

Summary: Chrome and Safari both zoom in on form (input, select, textarea) when it thinks the text is too small (less than 16px... which is huge). This turns user-scalable off. The only drawback is double-tap to zoom will be disabled as well, but given we already responsively design, I don't think thats an issue.

Test Plan: iOS simulator on secure and local test instances. Click on an input, no longer see UI zoom in.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D17714

src/view/page/PhabricatorBarePageView.php

@@ -72,7 +72,7 @@ class PhabricatorBarePageView extends AphrontPageView {
           'name' => 'viewport',
           'content' => 'width=device-width, '.
                        'initial-scale=1, '.
-                       'maximum-scale=1',
+                       'user-scalable=no',
         ));
     }