apply simplifications available via property-first model and new sugaring (auto property-initialization and classList.enable polyfill)

src/g-icon-button.html

@@ -14,16 +14,12 @@
   </template>
   <script>
     this.component({
-      created: function() {
-        this.srcAttributeChanged();
-        this.activeAttributeChanged();
-      },
       prototype: {
-        srcAttributeChanged: function() {
+        srcChanged: function() {
           this.$.icon.src = this.src;
         },
-        activeAttributeChanged: function() {
-          this.classList[this.active ? 'add' : 'remove']('selected');
+        activeChanged: function() {
+          this.classList.enable('selected', this.active);
         }
       }
     });

src/g-icon.html

@@ -11,12 +11,8 @@ license that can be found in the LICENSE file.
   </template>
   <script>
     this.component({
-      created: function(inSuper) {
-        this.srcAttributeChanged();
-      },
       prototype: {
-        // note: this is called asyncronously. can we live with this?
-        srcAttributeChanged: function() {
+        srcChanged: function() {
           this.$.icon.style.backgroundImage =
             this.src ? 'url(' + this.src + ')' : null;
         }