Resize images from corner in Chrome

I read this in WP help:
“The process of resizing images is fairly simple. There are usually two methods:

1) You can resize an image through the use of tools provided which allow you to manually shift the edges of an image to deform or resize the image. The best way is to grab a corner, not the edge, to resize the image. The corner “handle” will usually resize the image maintaining the overall height-width ratio. Check your manual for specific instructions.”

I’m working with Chrome 5.0.375.55 in mac book pro and I can’t resize the image manually. Only if i do that from Advanced Properties and calculate in %. In Firefox is working manually.

There is some coder or solution for this trouble?
I don’t want to use Firefox.

thank u