Permit google app engine to be installed in testing_support.

Permit google app engine to be installed in testing_support.

I recently needed to run presubmit tests in depot_tools, and I was helpfully told:

$ gcl presubmit mychange
... eliding stuff ...
Install google_appengine sdk in /scratch/scratch/chrome/depot_tools_git/testing_support or higher up

This was a lie. If you put google_appengine there, the same presubmit
tools that told you to install it there will fail you for numerous
style violations contained within appengine itself. This change makes
us ignore those by blacklisting google_appengine inside of
testing_support.

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=151210

[gavinp, 2012-08-12 17:58:32]

cmp, 

I came across this while working on my dirty-index change. What do you think?

[cmp, 2012-08-12 22:23:21]

lgtm, thanks!