Add paper-menu-button and its dependencies to third_party/polymer

third_party/polymer/v1_0/components/iron-behaviors/iron-button-state.html

Index: third_party/polymer/v1_0/components/iron-behaviors/iron-button-state.html
diff --git a/third_party/polymer/v1_0/components/iron-behaviors/iron-button-state.html b/third_party/polymer/v1_0/components/iron-behaviors/iron-button-state.html
index fc52e172f920d899737e5800564b8730cff3764e..11c03d76b2fc7dde0e1cd3e5e7a489dc37687360 100644
--- a/third_party/polymer/v1_0/components/iron-behaviors/iron-button-state.html
+++ b/third_party/polymer/v1_0/components/iron-behaviors/iron-button-state.html
@@ -91,6 +91,8 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
       'space:keyup': '_spaceKeyUpHandler',
     },
 
+    _mouseEventRe: /^mouse/,
+
     _tapHandler: function() {
       if (this.toggles) {
        // a tap is needed to toggle the active state
@@ -111,7 +113,33 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
       this.fire('change');
     },
 
-    _downHandler: function() {
+    _eventSourceIsPrimaryInput: function(event) {
+      event = event.detail.sourceEvent || event;
+
+      // Always true for non-mouse events....
+      if (!this._mouseEventRe.test(event.type)) {
+        return true;
+      }
+
+      // http://developer.mozilla.org/en-US/docs/Web/API/MouseEvent/buttons
+      if ('buttons' in event) {
+        return event.buttons === 1;
+      }
+
+      // http://developer.mozilla.org/en-US/docs/Web/API/MouseEvent/which
+      if (typeof event.which === 'number') {
+        return event.which < 2;
+      }
+
+      // http://developer.mozilla.org/en-US/docs/Web/API/MouseEvent/button
+      return event.button < 1;
+    },
+
+    _downHandler: function(event) {
+      if (!this._eventSourceIsPrimaryInput(event)) {
+        return;
+      }
+
       this._setPointerDown(true);
       this._setPressed(true);
       this._setReceivedFocusFromKeyboard(false);