Ninja - This is a command line build system which is much faster than building from IDEs such as MSVS or XCode.
gclient - This is a wrapper which lets us act on all the various projects as one - for instance, we use “gclient sync” and “gclient runhooks” often.
GYP - This generates our project files to use with Ninja, MSVS, and/or XCode. It is run by gclient, we don’t normally call it directly. .gyp files take the place of makefiles or build files from other projects. GYP stands for “Generate Your Projects”
Git, subversion - The base repository is using subversion, but many people use git on top of it. There is work in progress to move the entire repository over to git.
DiffMerge - A graphical tool to view diffs graphically on your own machine before commiting to your local branch. This can be hooked up to Git and Subversion (search for instructions on the web). There are other graphical diff viewers that we use, but this one will work on all main supported platforms (Win, Mac, Linux)
Editor extensions - Emacs has some custom extensions to make chromium development easier - http://code.google.com/p/chromium/wiki/Emacs (TODO: as we find others for other editors, add them here!)