[telemetry] bitmaptools as a standalone executable

The C++ binary implements simple per-pixel algorithms for SpeedIndex
computation. This allows us to achieve near real-time processing without
bringing external dependencies.

The bitmaptools binary needs to be built before it can be used.
The overhead of spawning a child process for each frame is about 3ms.

BUG=323813
TEST=telemetry bitmap_unittest

Original review: https://codereview.chromium.org/136793022
TBR=tonyg,maruel

Review URL: https://codereview.chromium.org/131563009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246361 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246361