Enable tools/CrashHandler again.

  - Defaults to on the bots, triggered off CHROME_HEADLESS=1 in the environment.
  - Defaults off otherwise.
  - Can be enabled by setting CHROME_HEADLESS=1 (weird) or GYP_DEFINES=skia_crash_handler=1.

BUG=skia:
R=borenet@google.com, mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/383813002
2 files changed