修复matrix2d的identity的获取方法。

source/bin/framework.d.ts

@@ -1744,7 +1744,6 @@ declare module es {
          * 储存在这个矩阵中的缩放
          */
         scale: Vector2;
-        static _identity: Matrix2D;
         /**
          * 构建一个矩阵
          * @param m11

source/bin/framework.js

@@ -4204,7 +4204,7 @@ var es;
              * 返回标识矩阵
              */
             get: function () {
-                return this._identity;
+                return new Matrix2D(1, 0, 0, 1, 0, 0);
             },
             enumerable: true,
             configurable: true
@@ -4415,7 +4415,6 @@ var es;
         Matrix2D.prototype.toString = function () {
             return "{m11:" + this.m11 + " m12:" + this.m12 + " m21:" + this.m21 + " m22:" + this.m22 + " m31:" + this.m31 + " m32:" + this.m32 + "}";
         };
-        Matrix2D._identity = new Matrix2D(1, 0, 0, 1, 0, 0);
         return Matrix2D;
     }());
     es.Matrix2D = Matrix2D;

source/src/Math/Matrix2D.ts

@@ -16,7 +16,7 @@ module es {
          * 返回标识矩阵
          */
         public static get identity(): Matrix2D {
-            return this._identity;
+            return new Matrix2D(1, 0, 0, 1, 0, 0);
         }
 
         /**
@@ -71,8 +71,6 @@ module es {
             this.m22 = value.y;
         }
 
-        static _identity: Matrix2D = new Matrix2D(1, 0, 0, 1, 0, 0);
-
         /**
          * 构建一个矩阵
          * @param m11