Always trigger tap for synthetic click events

Fixes #2212

@@ -111,6 +111,25 @@
     }
   }
 
+  function isSyntheticClick(ev) {
+    if (ev.type === 'click') {
+      // ev.detail is 0 for HTMLElement.click in most browsers
+      if (ev.detail === 0) {
+        return true;
+      }
+      // in the worst case, check that the x/y position of the click is within
+      // the bounding box of the target of the event
+      // Thanks IE 10 >:(
+      var t = Gestures.findOriginalTarget(ev);
+      var bcr = t.getBoundingClientRect();
+      // use page x/y to account for scrolling
+      var x = ev.pageX, y = ev.pageY;
+      return (x >= bcr.left && x <= bcr.right) &&
+        (y >= bcr.top && y <= bcr.bottom);
+    }
+    return false;
+  }
+
   var POINTERSTATE = {
     mouse: {
       target: null,
@@ -624,7 +643,7 @@
       var dy = Math.abs(e.clientY - this.info.y);
       var t = Gestures.findOriginalTarget(e);
       // dx,dy can be NaN if `click` has been simulated and there was no `down` for `start`
-      if (isNaN(dx) || isNaN(dy) || (dx <= TAP_DISTANCE && dy <= TAP_DISTANCE)) {
+      if (isNaN(dx) || isNaN(dy) || (dx <= TAP_DISTANCE && dy <= TAP_DISTANCE) || isSyntheticClick(e)) {
         // prevent taps from being generated if an event has canceled them
         if (!this.info.prevent) {
           Gestures.fire(t, 'tap', {

@@ -53,6 +53,16 @@
         assert.equal(foo._testRootTarget, div, 'foo root target');
       });
 
+      test('HTMLElement.click triggers tap', function() {
+        // make a mousedown *very* far away to tickle the distance check
+        var ev = new CustomEvent('mousedown');
+        ev.clientX = 1e8;
+        ev.clientY = 1e8;
+        app.dispatchEvent(ev);
+        app.click();
+        assert.equal(app._testLocalTarget, app, 'app local target');
+        assert.equal(app._testRootTarget, app, 'app root target');
+      });
     });
 
     suite('Event Setup and Teardown', function() {