apps: Last logcat section should be skipped when processing bugreport

Android bugreports may contain a "LAST LOGCAT" section.  This should be
skipped and the most recent logcat section should be processed.

BUG=chromium:591926
TEST=manually with bugreports
TEST=ran 'grunt test'

Change-Id: I4cd79c0c2cd185d202b4d74c21d969b637767e05
2 files changed