Merge 182576 to M26 beta branch.

Merge 182576 to M26 beta branch.
> Re-land "view permission" feature (r179916) with Mac Fix.
> 
> The feature review URL: http://crrev.com/12094034
> Mac fix review URL: http://crrev.com/12258023
> This CL also combines the extension_install_prompt changes reviewed at http://crrev.com/12220142
> 
> RootCause for Mac failure: Permission Prompt does not have a OK button. 
> And Chrome hangs while trying to create a OK button with empty string. 
> Solution: Remove |okButton_| when its title is empty and adjust 
> |cancelButton_|'s position. 
> The screenshot with the fix is uploaded at http://crbug.com/175071#c15 
> 
> BUG=170742, 175071
> TBR=finnur@chromium.org
> TBR=sky@chromium.org for http://crrev.com/12094034
> TBR=sail@chromium.org for http://crrev.com/12258023
> 
> 
> Review URL: https://chromiumcodereview.appspot.com/12212195

TBR=MHX348@motorola.com
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=183258