Added build[49-56]-b4 to win_gpu configuration on tryserver waterfall.
Added build[49-56]-b4 to win_gpu configuration on tryserver waterfall.

BUG=335851

Review URL: https://codereview.chromium.org/194063002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@256320 0039d316-1c4b-4281-b951-d872f2087c98

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