History WebUI: Unselect all items when pressing escape

Bug: 1142082
Change-Id: I87d4970e5e20e3f8950e6e5f25b843e9c8fa096c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2511857Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Commit-Queue: John Lee <johntlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#824978}

chrome/browser/resources/history/app.js

@@ -309,6 +309,11 @@ import './strings.js';
           e.preventDefault();
         }
       }
+
+      if (e.key === 'Escape') {
+        this.unselectAll();
+        e.preventDefault();
+      }
     },
 
     /** @private */