chromium64.py: Add BrowserTests
android.py: Support 4.4.2 build
chromium64.py: Remove special handling for v8 and remove mk64 for test-build
chromium64.py: Sync patch with latest changes

Branch aia/topic/64-bit/master recently got a lot of merge from
platform-dev, so this check-in deletes one redundant patch, and includes
all (4) rebased patches.
Besides, bootable/userfastboot is added into dirty_repos; the function
to patch code is enhanced so that error can be caught; makefile that may
be generated manually would be deleted before patching the code.