Version: 54.0.2837.0 a29577e8b1ed329373d426e85f679dfeb07a2979-refs/heads/master@{#413618} (64-bit)
OS: Windows (7,8,8.1,10),Linux (14.04 LTS),Mac OS X(10.10.5, 10.11.4)

What steps will reproduce the problem?
1) Launch chrome and navigate to chrome://md-settings/siteSettings
2) Now go to 'Notifications' and click on 'Add site exception'
3) Now enter any text in text box and delete it(Keep the text box empty) and observe the 'Add' button

Actual : Unnecessary 'Add' button is seen enabled even when text box is empty.
Expected : 'Add' button should be disabled when text box is empty.

This is a non-regression issue, seen from M-53 series as 'Add site exception' option appears from build # 53.0.2767.0

Kindly review the attached video and screenshot for reference.
 

Deleted: Actual_video.mov 5.1 MB

Actual_video.mov 5.1 MB Download

Deleted: Actual_screenshot.png 240 KB

	Actual_screenshot.png 240 KB View Download