UX: make composer resize work on touch devices (#7068)

* UX: make composer resize work on touch devices

This also replaces a vendor dependency with a small built-in resize mechanism.

* Make blue bar's larger padding specific to touch devices

vendor/assets/javascripts/div_resizer.js

@@ -1,99 +0,0 @@
-/**
-  This is a jQuery plugin to support resizing text areas.
-
-  Originally based off text area resizer by Ryan O'Dell : http://plugins.jquery.com/misc/textarea.js
-
-  @module $.fn.DivResizer
-**/
-
-var div, endDrag, grip, lastMousePos, min, mousePosition, originalDivHeight, originalPos, performDrag, startDrag, wrappedEndDrag, wrappedPerformDrag;
-div = void 0;
-originalPos = void 0;
-originalDivHeight = void 0;
-lastMousePos = 0;
-min = 230;
-grip = void 0;
-wrappedEndDrag = void 0;
-wrappedPerformDrag = void 0;
-
-startDrag = function(e, opts) {
-  div = $(e.data.el);
-  div.addClass('clear-transitions');
-  div.blur();
-  lastMousePos = mousePosition(e).y;
-  originalPos = lastMousePos;
-  originalDivHeight = div.height();
-  wrappedPerformDrag = (function() {
-    return function(e) {
-      return performDrag(e, opts);
-    };
-  })();
-  wrappedEndDrag = (function() {
-    return function(e) {
-      return endDrag(e, opts);
-    };
-  })();
-  $(document).mousemove(wrappedPerformDrag).mouseup(wrappedEndDrag);
-  return false;
-};
-
-performDrag = function(e, opts) {
-  $(div).trigger("div-resizing");
-
-  var size, sizePx, thisMousePos;
-  thisMousePos = mousePosition(e).y;
-  size = originalDivHeight + (originalPos - thisMousePos);
-  lastMousePos = thisMousePos;
-
-  var maxHeight = $(window).height();
-  if (opts.maxHeight) {
-    maxHeight = opts.maxHeight(maxHeight);
-  }
-  size = Math.min(size, maxHeight);
-  size = Math.max(min, size);
-  sizePx = size + "px";
-  if (typeof opts.onDrag === "function") {
-    opts.onDrag(sizePx);
-  }
-  div.height(sizePx);
-  if (size < min) {
-    endDrag(e, opts);
-  }
-  return false;
-};
-
-endDrag = function(e, opts) {
-  $(document).unbind("mousemove", wrappedPerformDrag).unbind("mouseup", wrappedEndDrag);
-  div.removeClass('clear-transitions');
-  div.focus();
-  if (typeof opts.resize === "function") {
-    opts.resize();
-  }
-  $(div).trigger("div-resized");
-  div = null;
-};
-
-mousePosition = function(e) {
-  return {
-    x: e.clientX + document.documentElement.scrollLeft,
-    y: e.clientY + document.documentElement.scrollTop
-  };
-};
-
-$.fn.DivResizer = function(opts) {
-  return this.each(function() {
-    var grippie, start, staticOffset;
-    div = $(this);
-    if (div.hasClass("processed")) return;
-    div.addClass("processed");
-    staticOffset = null;
-    start = function() {
-      return function(e) {
-        return startDrag(e, opts);
-      };
-    };
-    grippie = div.prepend("<div class='grippie'></div>").find('.grippie').bind("mousedown", {
-      el: this
-    }, start());
-  });
-};