fixed #2723: Hide url address bar for mobile browser

For example:

--1 your design resolution size is 320*480
cc.EGLView.getInstance().setDesignResolutionSize(320,480,cc.RESOLUTION_POLICY.SHOW_ALL);

--2 set viewport

<meta name="viewport" content="width=320,user-scalable=no".....

when the design  height bigger than  clientHeight, that url address bar will hide in iphone safari and android default browser