Refactor ghost click code

Use Polymer.Debounce to properly debounce on quick taps
Use 2500ms timeout (from 0.5), 500ms is too short in the wild

src/standard/gestures.html

@@ -23,8 +23,8 @@
   // number of last N track positions to keep
   var TRACK_LENGTH = 2;
 
-  // Disabling "mouse" handlers for 500ms is enough
-  var MOUSE_TIMEOUT = 500;
+  // Disabling "mouse" handlers for 2500ms is enough
+  var MOUSE_TIMEOUT = 2500;
   var MOUSE_EVENTS = ['mousedown', 'mousemove', 'mouseup', 'click'];
 
   // touch will make synthetic mouse events
@@ -48,39 +48,41 @@
     }
   };
 
-  function ignoreMouse(set) {
-    // manual debounce
-    if (set && POINTERSTATE.touch.mouseIgnoreId !== -1) {
-      return;
-    }
+  function setupTeardownMouseCanceller(setup) {
     for (var i = 0, en; i < MOUSE_EVENTS.length; i++) {
       en = MOUSE_EVENTS[i];
-      if (set) {
+      if (setup) {
         document.addEventListener(en, mouseCanceller, true);
       } else {
         document.removeEventListener(en, mouseCanceller, true);
       }
     }
-    if (set) {
-      // disable MOUSE_CANCELLER after MOUSE_TIMEOUT ms
-      POINTERSTATE.mouse.mouseIgnoreId = setTimeout(ignoreMouse, MOUSE_TIMEOUT);
-    } else {
-      POINTERSTATE.mouse.target = null;
-      POINTERSTATE.touch.mouseIgnoreId = -1;
+  }
+
+  function ignoreMouse() {
+    if (!POINTERSTATE.mouse.mouseIgnoreJob) {
+      setupTeardownMouseCanceller(true);
     }
+    var unset = function() {
+      setupTeardownMouseCanceller();
+      POINTERSTATE.mouse.target = null;
+      POINTERSTATE.mouse.mouseIgnoreJob = null;
+    };
+    POINTERSTATE.mouse.mouseIgnoreJob =
+      Polymer.Debounce(POINTERSTATE.mouse.mouseIgnoreJob, unset, MOUSE_TIMEOUT);
   }
 
   var POINTERSTATE = {
     tapPrevented: false,
     mouse: {
       target: null,
+      mouseIgnoreJob: null
     },
     touch: {
       x: 0,
       y: 0,
       id: -1,
-      scrollDecided: false,
-      mouseIgnoreId: -1
+      scrollDecided: false
     }
   };