i.e. to not wait for the key to be fully pressed and released.
I know this method works in a game I play so I know it is technically possible.
The games that you're talking about were programmed specifically to behave this way, Chrome is not.
Chrome is an open-source program however, so it would be possible to modify the source code and recompile it to behave the way you want, but it would take some advanced developer skills.
Here's where you can access the Chrome source code : http://www.chromium.org/Home
It would only be possible to enable this through a Chrome plugin, if Google had enabled such a feature already through the plugin API.
In Microsoft Windows, mouse button press is actually a start of three separate actions:
As you see, in order to recognize #2 and #3 above, Windows waits for the mouse button release and a short pause afterwards, before it sends "mouse was single-clicked" message to an application. Games that you mention, however, listen to the "mouse was pressed" message, which is sent immediately as a mouse button is pressed down.
Google Chrome must also support double click and drag-n-drop, therefore it cannot just assume that mouse press is a mouse single click. Thus what you ask for is probably impossible.
To understand this better, read about fastbuttons here http://code.google.com/mobile/articles/fast_buttons.html