Edit: I just discovered a problem in the grub.cfg included in efi.zip that broke the Chrome application menu. I uploaded a new version of efi.zip that fixes this issue.
Note: This tutorial assumes that you have followed the directions at (http://chromeos.hexxeh.net/) and already have Chrome OS Flow loaded onto a 2GB or larger usb flash drive. This drive will be further known as the ChromeOS Drive.
Note++: It may be possible to get Chrome OS Flow working on other Intel-based MacBooks/MacBook Pros, but for all intents and purposes, this tutorial is for getting Chrome OS Flow to run on a Intel Core 2 Duo based MacBook that uses the Intel GMA 950 chipset. Feel free to use my work as a starting point if you would like to try to get it working with other models.
What Hardware You Will Need
An additional usb flash drive. (Any size or model should work.). This drive will be further known as the Bootloader Drive.
Hardware You Might Need
A usb hub or usb extender cable. (These may be necessary because having two usb flash drives plugged into your MacBook’s two usb ports may either be a little cramped or not physically possible w/o using a hub or extender cable.)
Preparing the Bootloader Drive
Open Disk Utility, select your Bootloader Drive, click the Erase tab and format your drive as “MS-DOS (FAT)”.
Download and extract the contents of this file, efi.zip.
Copy the “efi” folder to the root of the Bootloader Drive.
Plugging Drives Into Correct USB Port
The Bootloader Drive must be plugged into the first usb port (the first port from the left) and the ChromeOS Drive must be plugged into the second usb port.
Booting Chrome OS Flow
Restart OSX and immediately hold down the Option key.
Choose “EFI Boot”.
The GRUB bootloader should appear, automatically load Chrome OS Flow, display the splash screen and then stop at the Chrome OS login screen.
Logging into Chrome OS Flow
You can either log in using your gmail account username and password or by using “facepunch” as both the username and password. Enjoy.