Roll Polymer to 1.3.1

third_party/polymer/v1_0/components-chromium/iron-selector/iron-selection-extracted.js

Index: third_party/polymer/v1_0/components-chromium/iron-selector/iron-selection-extracted.js
diff --git a/third_party/polymer/v1_0/components-chromium/iron-selector/iron-selection-extracted.js b/third_party/polymer/v1_0/components-chromium/iron-selector/iron-selection-extracted.js
index 9c9d1ec9f435edc5c29a3247539b00cc3d4dfda5..65083e9885e5cf5f2181480cb48a3c88006a9cc2 100644
--- a/third_party/polymer/v1_0/components-chromium/iron-selector/iron-selection-extracted.js
+++ b/third_party/polymer/v1_0/components-chromium/iron-selector/iron-selection-extracted.js
@@ -55,16 +55,19 @@
      */
     setItemSelected: function(item, isSelected) {
       if (item != null) {
-        if (isSelected) {
-          this.selection.push(item);
-        } else {
-          var i = this.selection.indexOf(item);
-          if (i >= 0) {
-            this.selection.splice(i, 1);
+        if (isSelected !== this.isSelected(item)) {
+          // proceed to update selection only if requested state differs from current
+          if (isSelected) {
+            this.selection.push(item);
+          } else {
+            var i = this.selection.indexOf(item);
+            if (i >= 0) {
+              this.selection.splice(i, 1);
+            }
+          }
+          if (this.selectCallback) {
+            this.selectCallback(item, isSelected);
           }
-        }
-        if (this.selectCallback) {
-          this.selectCallback(item, isSelected);
         }
       }
     },