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

third_party/polymer/v1_0/reproduce.sh

Index: third_party/polymer/v1_0/reproduce.sh
diff --git a/third_party/polymer/v1_0/reproduce.sh b/third_party/polymer/v1_0/reproduce.sh
index 331164c3ee8dbfd83454f8b6153b1e0ced79cb51..ec932c2efb917b0e8bf877e02b8acccb316f5f2e 100755
--- a/third_party/polymer/v1_0/reproduce.sh
+++ b/third_party/polymer/v1_0/reproduce.sh
@@ -40,6 +40,10 @@ rm -rf components/promise-polyfill
 rm -rf components/iron-ajax
 rm -rf components/iron-form
 
+# Remove iron-image as it's only a developer dependency of iron-dropdown.
+# https://github.com/PolymerElements/iron-dropdown/pull/17
+rm -rf components/iron-image
+
 # Make checkperms.py happy.
 find components/*/hero.svg -type f -exec chmod -x {} \;
 find components/iron-selector -type f -exec chmod -x {} \;