lazy inject on client

Author: yyx990803

lib/component-normalizer.js

@@ -39,6 +39,7 @@ module.exports = function normalizeComponent (
   var hook
   if (isServer) {
     hook = function (context) {
+      // context is injected if this is a cached call
       if (!context && typeof __VUE_SSR_CONTEXT__ !== 'undefined') {
         context = __VUE_SSR_CONTEXT__
       }
@@ -51,9 +52,14 @@ module.exports = function normalizeComponent (
     // never gets called
     options._ssrRegister = hook
   } else if (injectStyles) {
-    var cssModules = injectStyles({})
-    if (cssModules) {
-      hook = function () {
+    var injected = false // only need to inject once on the client
+    var cssModules
+    hook = function () {
+      if (!injected) {
+        injected = true
+        cssModules = injectStyles({})
+      }
+      if (cssModules) {
         for (var key in cssModules) {
           this[key] = cssModules[key]
         }