remove unnecessary html canvas in example

examples/shell.emscripten.html

@@ -14,8 +14,6 @@
       .emscripten { padding-right: 0; margin-left: auto; margin-right: auto; display: block; }
       div.emscripten { text-align: center; }
       div.emscripten_border { border: 1px solid black; }
-      /* the canvas *must not* have any border or padding, or mouse coords will be wrong */
-      canvas.emscripten { border: 0px none; background-color: black; }
 
       #emscripten_logo {
         display: inline-block;
@@ -111,9 +109,6 @@
 </div>
 
 
-<div class="emscripten_border">
-    <canvas class="emscripten" id="canvas" oncontextmenu="event.preventDefault()" tabindex=-1></canvas>
-</div>
 <textarea id="output" rows="8"></textarea>
 
 <script type='text/javascript'>
@@ -141,16 +136,6 @@
             }
           };
         })(),
-        canvas: (function() {
-          var canvas = document.getElementById('canvas');
-
-          // As a default initial behavior, pop up an alert when webgl context is lost. To make your
-          // application robust, you may want to override this behavior before shipping!
-          // See http://www.khronos.org/registry/webgl/specs/latest/1.0/#5.15.2
-          canvas.addEventListener("webglcontextlost", function(e) { alert('WebGL context lost. You will need to reload the page.'); e.preventDefault(); }, false);
-
-          return canvas;
-        })(),
         setStatus: function(text) {
           if (!Module.setStatus.last) Module.setStatus.last = { time: Date.now(), text: '' };
           if (text === Module.setStatus.last.text) return;