Add support to lkgr_finder.py for watching multiple masters.
Add support to lkgr_finder.py for watching multiple masters.

Add chromium.chrome Google Chrome Linux x64 to LKGR to
ensure LKGR doesn't roll when Google Chrome Linux x64
compile is broken.  This also verifies this change works
when at least two masters are configured.

In preparation for sharding the main Chromium waterfall
into multiple masters, update the LKGR finder script to
add support for watching multiple masters.

This CL works by inserting an additional dictionary where
possible to contain keys for each of the masters.  And in
FindLKGRCandidate() the master and builder are simply
concatenated.

After this change, we will be able to more generally support
extending LKGR to cover more masters/builders/steps beyond
the split masters and chromium.chrome Google Chrome Win.

R=szager@chromium.org,nsylvain@chromium.org

Review URL: http://codereview.chromium.org/10383024

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@135570 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build