I'm seeing the following error:
build/gyp_pdfium
Updating projects from gyp files...
/usr/local/Cellar/python/2.7.11/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python: can't open file '../tools/clang/scripts/update.py': [Errno 2] No such file or directory
gyp: Call to 'python ../tools/clang/scripts/update.py --print-revision' returned exit status 2 while in /private/tmp/pdfium20151228-46857-htvxjl/build/all.gyp.
I'm not sure how to get tools/clang/scripts/update.py. Googling didn't turn up any clear fix.