Fix RebaselineTest._copy_existing_baseline() to not assume that fallback directory names match port…

Fix RebaselineTest._copy_existing_baseline() to not assume that fallback directory names match port names

Port.baseline_version_dir() provides the default baseline path and this is not
guaranteed to match the port name. So instead of making this assumption, search
for a matching port.

This is required to allow the 'chromium-' prefix to be removed from port names
independently of renaming the fallback directories.

BUG=231188
R=ojan

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=152596

[Dirk Pranke, 2013-06-17 19:35:22]

lgtm.

[commit-bot: I haz the power, 2013-06-17 23:43:31]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/steveblock@chromium.org/16888010/1

[commit-bot: I haz the power, 2013-06-18 00:48:21]

Change committed as 152596