cc: Remove the need for a RasterTaskSet to track "required to activate" property in PixelBufferRasterWorkerPool.

Provides a ~15% performance improvement to ScheduleTasks by instead using
RasterTaskState to track this property.

BUG=269841
TEST=cc_perftests --gtest_filter=RasterWorkerPoolPerfTests/RasterWorkerPoolPerfTest.ScheduleTasks/0

Review URL: https://codereview.chromium.org/171233016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254855 0039d316-1c4b-4281-b951-d872f2087c98
Use ninja as the default GYP generator on FreeBSD.

While here, consistently use a single 'if' statement to set this
environment variable.

BUG=

Review URL: https://codereview.chromium.org/176843005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254856 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254856