feat: remove MapWrapper.clear().

It's the same in Dart and JavaScript.

modules/angular2/src/change_detection/pipes/iterable_changes.ts

@@ -621,7 +621,7 @@ class _DuplicateMap {
 
   get isEmpty(): boolean { return MapWrapper.size(this.map) === 0; }
 
-  clear() { MapWrapper.clear(this.map); }
+  clear() { this.map.clear(); }
 
   toString(): string { return '_DuplicateMap(' + stringify(this.map) + ')'; }
 }

modules/angular2/src/core/compiler/compiler.ts

@@ -52,8 +52,8 @@ export class CompilerCache {
   }
 
   clear(): void {
-    MapWrapper.clear(this._cache);
-    MapWrapper.clear(this._hostCache);
+    this._cache.clear();
+    this._hostCache.clear();
   }
 }
 

modules/angular2/src/facade/collection.dart

@@ -43,9 +43,6 @@ class MapWrapper {
   static void delete(Map m, k) {
     m.remove(k);
   }
-  static void clear(Map m) {
-    m.clear();
-  }
   static void clearValues(Map m) {
     for (var k in m.keys) {
       m[k] = null;

modules/angular2/src/facade/collection.ts

@@ -67,7 +67,6 @@ export class MapWrapper {
   static forEach<K, V>(m: Map<K, V>, fn: /*(V, K) => void*/ Function) { m.forEach(<any>fn); }
   static size(m: Map<any, any>) { return m.size; }
   static delete<K>(m: Map<K, any>, k: K) { m.delete(k); }
-  static clear(m: Map<any, any>) { m.clear(); }
   static clearValues(m: Map<any, any>) { _clearValues(m); }
   static iterable(m) { return m; }
   static keys<K>(m: Map<K, any>): List<K> { return m.keys(); }

modules/angular2/src/render/dom/shadow_dom/util.ts

@@ -60,8 +60,8 @@ export function shimCssForComponent(cssText: string, componentId: string): strin
 
 // Reset the caches - used for tests only
 export function resetShadowDomCache() {
-  MapWrapper.clear(_componentUIDs);
+  _componentUIDs.clear();
   _nextComponentUID = 0;
-  MapWrapper.clear(_sharedStyleTexts);
+  _sharedStyleTexts.clear();
   _lastInsertedStyleEl = null;
 }

modules/angular2/test/change_detection/pipes/keyvalue_changes_spec.ts

@@ -98,7 +98,7 @@ export function main() {
             .toEqual(kvChangesAsString(
                 {map: ['a', 'd'], previous: ['a', 'b[BB->null]', 'd'], removals: ['b[BB->null]']}));
 
-        MapWrapper.clear(m);
+        m.clear();
         changes.check(m);
         expect(changes.toString())
             .toEqual(kvChangesAsString(