Roll Polymer from 1.5.0 -> 1.6.0 to pick up native CSS custom props

third_party/polymer/v1_0/components-chromium/paper-dropdown-menu/paper-dropdown-menu-extracted.js

Index: third_party/polymer/v1_0/components-chromium/paper-dropdown-menu/paper-dropdown-menu-extracted.js
diff --git a/third_party/polymer/v1_0/components-chromium/paper-dropdown-menu/paper-dropdown-menu-extracted.js b/third_party/polymer/v1_0/components-chromium/paper-dropdown-menu/paper-dropdown-menu-extracted.js
index 4965059815cf0faac2383c40c20a1f0beeafe341..1f107e2a1a62b03ac7ba702e35f6f524f19428a6 100644
--- a/third_party/polymer/v1_0/components-chromium/paper-dropdown-menu/paper-dropdown-menu-extracted.js
+++ b/third_party/polymer/v1_0/components-chromium/paper-dropdown-menu/paper-dropdown-menu-extracted.js
@@ -79,6 +79,17 @@
           },
 
           /**
+           * By default, the dropdown will constrain scrolling on the page
+           * to itself when opened.
+           * Set to true in order to prevent scroll from being constrained
+           * to the dropdown when it opens.
+           */
+          allowOutsideScroll: {
+            type: Boolean,
+            value: false
+          },
+
+          /**
            * Set to true to disable the floating label. Bind this to the
            * `<paper-input-container>`'s `noLabelFloat` property.
            */
@@ -216,7 +227,7 @@
           if (!selectedItem) {
             value = '';
           } else {
-            value = selectedItem.label || selectedItem.textContent.trim();
+            value = selectedItem.label || selectedItem.getAttribute('label') || selectedItem.textContent.trim();
           }
 
           this._setValue(value);