Builders switching from make to ninja will clobber on this.
Need to clobber everything due to an IDL change in r154579 (blink)
Need to clobber everything due to gen file moves in r175513 (Blink)
Clobber to get rid of obselete test plugin after r248358
Clobber to rebuild GN files for V8
Clobber to get rid of stale generated mojom.h files
Need to clobber everything due to build_nexe change in nacl r13424
[chromium-dev] PSA: clobber build needed for IDR_INSPECTOR_* compil...
blink_resources.grd changed: crbug.com/400860
ninja dependency cycle: crbug.com/408192
Clobber to fix missing NaCl gyp dependencies (crbug.com/427427).
Another clobber for missing NaCl gyp deps (crbug.com/427427).
Clobber to fix GN not picking up increased ID range (crbug.com/444902)
Remove NaCl toolchains from the output dir (crbug.com/456902)
CLobber all to fix GN breakage (crbug.com/736215)
The Great Blink mv for source files (crbug.com/768828)
Clobber to workaround buggy .ninja_deps cycle (crbug.com/934404)
Clobber to flush stale generated files. See crbug.com/1406628
Clobber to flush old .ninja_log files for updating ninja. See crbug.com/1406628#c14