Enable crashpad for Mac.

This follows the same logic as using breakpad in linux with flags --enable_crash-reporter and --crash-dumps-dir folders.

For headless_shell target, we need to include the Helper crashpad_handler in the build. For --headless, this is already available in the framework bundle.

BUG=687407

Review-Url: https://codereview.chromium.org/2816593006
Cr-Commit-Position: refs/heads/master@{#464289}
3 files changed