chore: kill ListWrapper.create() and .push().

These wrappers are not natively understood by
ts2dart. Removing them will improve Dart2JS
compilation due to fewer megamorphic calls to List
functions.

It also makes Angular code more succinct and
improves type safety in Angular due to better type
inference of the Array component type.

This change exposed several bugs in Angular.

modules/angular2/src/http/headers.ts

@@ -33,8 +33,8 @@ export class Headers {
       this._headersMap = MapWrapper.createFromStringMap(headers);
       MapWrapper.forEach(this._headersMap, (v, k) => {
         if (!isListLikeIterable(v)) {
-          var list = ListWrapper.create();
-          ListWrapper.push(list, v);
+          var list = [];
+          list.push(v);
           MapWrapper.set(this._headersMap, k, list);
         }
       });
@@ -42,8 +42,8 @@ export class Headers {
   }
 
   append(name: string, value: string): void {
-    var list = MapWrapper.get(this._headersMap, name) || ListWrapper.create();
-    ListWrapper.push(list, value);
+    var list = MapWrapper.get(this._headersMap, name) || [];
+    list.push(value);
     MapWrapper.set(this._headersMap, name, list);
   }
 
@@ -61,11 +61,11 @@ export class Headers {
 
   // TODO: this implementation seems wrong. create list then check if it's iterable?
   set(header: string, value: string | List<string>): void {
-    var list = ListWrapper.create();
+    var list = [];
     if (!isListLikeIterable(value)) {
-      ListWrapper.push(list, value);
+      list.push(value);
     } else {
-      ListWrapper.push(list, ListWrapper.toString((<List<string>>value)));
+      list.push(ListWrapper.toString((<List<string>>value)));
     }
 
     MapWrapper.set(this._headersMap, header, list);
@@ -73,9 +73,7 @@ export class Headers {
 
   values() { return MapWrapper.values(this._headersMap); }
 
-  getAll(header: string): Array<string> {
-    return MapWrapper.get(this._headersMap, header) || ListWrapper.create();
-  }
+  getAll(header: string): Array<string> { return MapWrapper.get(this._headersMap, header) || []; }
 
   entries() { throw new BaseException('"entries" method is not implemented on Headers class'); }
 }