MD Settings: mouse movements should focus cr-action-menu items

ui/webui/resources/cr_elements/cr_action_menu/cr_action_menu.js

Index: ui/webui/resources/cr_elements/cr_action_menu/cr_action_menu.js
diff --git a/ui/webui/resources/cr_elements/cr_action_menu/cr_action_menu.js b/ui/webui/resources/cr_elements/cr_action_menu/cr_action_menu.js
index 9f58dc4f6cd9079f59c2ee05364b0f1f5aef5e46..8e82b3dff53ce14fe06b6863e58fc2e42d30cc40 100644
--- a/ui/webui/resources/cr_elements/cr_action_menu/cr_action_menu.js
+++ b/ui/webui/resources/cr_elements/cr_action_menu/cr_action_menu.js
@@ -32,6 +32,7 @@ Polymer({
 
   listeners: {
     'keydown': 'onKeyDown_',
+    'mousemove': 'onMouseMove_',
     'tap': 'onTap_',
   },
 
@@ -83,6 +84,25 @@ Polymer({
     e.preventDefault();
   },
 
+  debounceFlusher_: null,
+
+  onMouseMove_: function(e) {
+    var target = e.target;
+
+    if(!this.debounceFlusher_) {

[scottchen, 2017/04/04 20:43:12]

Need this, otherwise if the user keeps moving their mouse on the menu non-stop,
the hover will never change target.

+      this.debounceFlusher_ = setTimeout(function(){
+        this.flushDebouncer('cr-action-menu-mousemove');
+        this.debounceFlusher_ = null;
+      }.bind(this), 10);
+    }
+
+    this.debounce('cr-action-menu-mousemove', function(){
+      if(target.classList.contains('dropdown-item') && 
+          target != document.activeElement)
+        target.focus();
+    }.bind(this), 10);
+  },
+
   /**
    * @param {number} step -1 for getting previous option (up), 1 for getting
    *     next option (down).