Reorganize directory structures

Signed-off-by: Sean Du <do4suki@gmail.com>

static/js/button.js

@@ -1,69 +0,0 @@
-var Button = function() {
-};
-
-Button.TAPPED = 'tapped';
-
-Button.initialize = function(element, onTap) {
-  var touchInfo = null;
-
-  if (typeof onTap === 'function') {
-    onTap = onTap.bind(element);
-  } else {
-    onTap = function() {};
-  }
-
-  function d2(x1, y1, x2, y2) {
-    var dx = x2 - x1, dy = y2 - y1;
-    return dx * dx + dy * dy;
-  }
-
-  function startTap(touch) {
-    touchInfo = {startX: touch.clientX, startY: touch.clientY, tapped: false};
-    element.classList.add(Button.TAPPED);
-  }
-
-  function endTap() {
-    element.classList.remove(Button.TAPPED);
-    touchInfo = null;
-  }
-
-  element.addEventListener('touchstart', function(e) {
-    startTap(e.changedTouches[0]);
-    e.preventDefault();
-  });
-
-  element.addEventListener('touchmove', function(e) {
-    if (touchInfo) {
-      var x0 = touchInfo.startX;
-      var y0 = touchInfo.startY;
-      var x = e.changedTouches[0].clientX;
-      var y = e.changedTouches[0].clientY;
-
-      var current = document.elementFromPoint(x, y);
-
-      const THRESHOLD_SQ_PX = 50 * 50;
-      if (!element.contains(current) || d2(x0, y0, x, y) > THRESHOLD_SQ_PX) {
-        endTap();
-      }
-    }
-
-    e.preventDefault();
-  });
-
-  element.addEventListener('touchend', function(e) {
-    if (touchInfo && !touchInfo.tapped) {
-      touchInfo.tapped = true;
-      onTap();
-    }
-
-    endTap();
-    e.preventDefault();
-  });
-
-  element.addEventListener('touchcancel', function(e) {
-    endTap();
-    e.preventDefault();
-  });
-
-  return element;
-};