Add the ability to select a source image to use in the code.

experimental/webtry/templates/content.html

 
 <section id=content>
+
+  <template id=sourcesTemplate>
+      <button id="" class=source><img width=64 height=64 src=''></button>
+  </template>
+  <input type="checkbox" id="enableSource" data-id="{{.Source}}"> Use an input bitmap.
+  <br>
+  <button id=selectedSource></button>
+  <pre id=sourceCode>SkBitmap source;</pre>
+  <div id=chooseSource>
+    Choose an image below or upload a new one to use as an input bitmap.
+    <div id="chooseList">
+    </div>
+    <form action="/sources/" method="post" accept-charset="utf-8" enctype="multipart/form-data">
+      <input type="file" accept="image/*" name="upload" value="" id="upload">
+      <input type="submit" value="Add Image">
+    </form>
+  </div>
+
   <pre>
     <textarea spellcheck=false name='code' id='code' rows='15' cols='100'>{{.Code}}</textarea>
   </pre>
 
   <input type='button' value='Run' id='run'>
   <a href='{{if .Hash}}/c/{{.Hash}}{{end}}' target=_blank id=permalink>Share</a>
 
   <input type='button' value='Embed' id='embedButton' disabled/>
   <input type="text" value="" id="embed" readonly style="display:none;">
+  <br>
 
   <p>
   <img  touch-action='none' class='zoom' id='img' src='{{if .Hash}}/i/{{.Hash}}.png{{end}}'/>
   </p>
   <p id='zoomHex'></p>
 
   <h2>Warnings and Errors</h2>
   <pre><code id='output'></code></pre>
   <h2>Runtime output</h2>
   <pre id='stdout'></pre>
 
 </section>