Fix LASTCHANGE in when merging a release.

The previous changes to merge_from_chromium caused the script to
crash when generating LASTCHANGE for a release.
This fixes the crash by using the SHA1 of the upstream merge
parent to generate LASTCHANGE.

Change-Id: I34ff309400135bb09a91e7e32a9eb1aea1e8c310
(cherry picked from commit f2e9853ae82a5b792ddf1af7c7d8924e9cb8c9b4)
1 file changed
tree: a1a58bd9d8a19c89434fa7015cba9cb149e508ea
  2. chromium/
  3. nullwebview/