Enabled the App Info Dialog on the chrome://extensions page

Enabled the App Info Dialog on the chrome://extensions page behind the
--enable-extension-info-dialog flag. With the flag enabled, the
'Permissions' link to an 'Info' link and making it launch the App Info
dialog. Also modified the dialog slightly so that it works with
extensions (as well as apps), and added some extra configuration
parameters so that the dialog can be customised slightly when
displayed outside of the app list. Not enabled on Mac (the flag is not
available).

Also extended BubbleFrameView to allow the ClientView to extend to the
top of the dialog when WidgetDelegate::ShouldShowWindowTitle is false,
even if the close button is being displayed.

Based on www.crrev.com/475643002.

BUG=395495

Review URL: https://codereview.chromium.org/471813002

Cr-Commit-Position: refs/heads/master@{#298355}
20 files changed