Update Polymer components.

third_party/polymer/components/iron-flex-layout/.bower.json

Index: third_party/polymer/components/iron-flex-layout/.bower.json
diff --git a/third_party/polymer/components/iron-flex-layout/.bower.json b/third_party/polymer/components/iron-flex-layout/.bower.json
index 3487142e11399a3d649b13e44f068b1666e113fc..07a77908f7746c2546e56a4b289a522a31540adf 100644
--- a/third_party/polymer/components/iron-flex-layout/.bower.json
+++ b/third_party/polymer/components/iron-flex-layout/.bower.json
@@ -1,6 +1,6 @@
 {
   "name": "iron-flex-layout",
-  "version": "1.3.2",
+  "version": "1.3.7",
   "description": "Provide flexbox-based layouts",
   "keywords": [
     "web-components",
@@ -27,13 +27,16 @@
     "webcomponentsjs": "webcomponents/webcomponentsjs#^0.7.0",
     "web-component-tester": "^4.0.0"
   },
+  "pages": {
+    "Flexbox layout guide": "GUIDE.md"
+  },
   "ignore": [],
   "homepage": "https://github.com/polymerelements/iron-flex-layout",
-  "_release": "1.3.2",
+  "_release": "1.3.7",
   "_resolution": {
     "type": "version",
-    "tag": "v1.3.2",
-    "commit": "a8ac9fb8984dc456aeaaf5c8f88d0f9e6991a3c5"
+    "tag": "v1.3.7",
+    "commit": "2a9c084c933e87469824b69f3faadfcba12efbcd"
   },
   "_source": "https://github.com/polymerelements/iron-flex-layout.git",
   "_target": "^1.0.0",