On Mac OS X Yosemite the green icon in every window:
is by default used to make the application full screen.
How do I make it work the same way as in previous versions of Mac OS X, i.e. to maximize the window?
As the below mentioned solution is application-based (i.e. only works for apps like Google Chrome), another way to approach this problem is to ignore the maximize button entirely and to install the open source app spectacle which offers the keyboard shortcut:
⌘ + ⌥ + F
It also has some other nice features, too. And it works for all apps.
In order to maximize the window so that it fills the visible window content, use:
⌥ + Click on green icon
In order to maximize the window both in width and height to the current desktop for applications like Google Chrome use:
⌥ + ⇧ + Click on green icon
You notice the change of behaviour of the button in the way it changes its content from two the arrows to a plus sign.
Zoom function can now be performed more easily — by double-clicking window title. You don't need to precisely aim at the small green button anymore, which I believe is the reason it has been converted into full screen button by default.
If you hold the shift key and double-click the window title Applications that use "smart zoom" will be forced to do full screen zoom. Smart zoom was a (much missed) OS X window behavior where, rather than fill all of an immense display, the window would enlarge based on its "needs". Apple removed smart zoom behavior form its own apps, but Chrome still does this.
So, in general, make the painful switch to working with the title bar and ignore the green button except for the rare times you truly want full screen. If you get 'smart zoom' and want to fill screen instead, repeat but hold shift key.
I've already posted in a similar topic - Check out the free"spectacle" that has a bunch of handy window management shortcuts.. Running that app adds cmd+option+F for true full screen with status bar.
PS. I really hate that instead of adding the "option" key for the current maximize to full screen behavior they just replaced the button that people used for years.
PPS. I tried double clicking windows, it does not work as expected, at best it somehow resizes the screen, so it's maximum height, but it does not fill the entire width of the screen. A chrome window with tabs ignores double clicks.
PPPS. Option+click does not work as expected either - it does the same thing as double clicking the window - the window resizes in vertical direction, but not in horizontal one. (I have two monitor system, and it does not fill either one of them).
So, pre yosemite, holding "Shift + Left Click" would alternate between the current dimensions and what they'd be if you were to maximize the window to the fully available dimensions.
The "Option + Left Click" alternates between window sizes (the last and the full-height of the screen (less the dock). Also, regardless of where the page is focused, after using the option click, the focus reverts to the upper left of the page (fun-fact).
Another thing to note is if you have more than one window open the "option + left-click" will maximize the secondary window, and depending its current dimensions, adhere to the same scale as if you were to hold down the Option key when click-dragging the corner of the window to manually resize the frame (scales on a fixed ratio).
To answer your question try "Option + Left-click" and/or "Shift + Left-click". Then perhaps try them together ;)