Fix problem with Polyfills

packages/aws-amplify/src/Cache/StorageCache.ts

@@ -129,7 +129,7 @@ export default class StorageCache {
             logger.warn(`Don't try to configure keyPrefix!`);
         }
 
-        this.config = Object.assign({}, this.config, config);
+        this.config = Object.assign({}, this.config, config, config.Cache);
         this.checkConfig();
         return this.config;
     }

packages/aws-amplify/src/Cache/types/Cache.ts

@@ -63,6 +63,8 @@ export interface CacheConfig {
     defaultPriority?: number;
 
     storage?: Storage;
+
+    Cache?: Cache;
 }
 
 export interface CacheItem {

packages/aws-amplify/src/Common/Polyfills/Polyfills.ts

@@ -11,25 +11,20 @@
  * and limitations under the License.
  */
 
-(<any>global).window = (<any>global).window || {
-    setTimeout,
-    clearTimeout,
-    WebSocket: (<any>global).WebSocket,
-    ArrayBuffer: (<any>global).ArrayBuffer,
-    addEventListener(){ },
-    navigator: { onLine: true }
-};
-(<any>global).localStorage = (<any>global).localStorage || {
-    store: {},
-    getItem(key){
-        if (this.store[key]) {
-            return this.store[key];
-        }
-        return null;
-    },
-    setItem(key, value){
-        this.store[key] = value;
-    },
-    removeItem(key){ delete this.store[key]; }
-};
+
+import InMemoryCache from '../../Cache/InMemoryCache';
+
+if (!(<any>global).window) {
+    (<any>global).window = {
+        setTimeout,
+        clearTimeout,
+        WebSocket: (<any>global).WebSocket,
+        ArrayBuffer: (<any>global).ArrayBuffer,
+        addEventListener(){ },
+        navigator: { onLine: true }
+    };
+}
+if (!(<any>global).localStorage){
+    (<any>global).localStorage = InMemoryCache;
+}