Add landmine due to generated file move in Blink r175513

Blink generated file move requires a clobber to avoid using stale
generated files.

This should have been included in the Blink roll, but we
didn't realize this was needed, so we failed to advise the
gardener (sorry!):
Blink roll 175512:175568
https://codereview.chromium.org/317183002/

See discussion at:
https://code.google.com/p/chromium/issues/detail?id=381111#c4

BUG=381111
TBR=dcheng
TBR=peter

Review URL: https://codereview.chromium.org/316343003

git-svn-id: http://src.chromium.org/svn/trunk/src/build@275406 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

get_landmines.py

@@ -50,6 +50,7 @@ def print_landmines(target):
     print "Switched win from VS2010 to VS2013."
     print "Update to VS2013 Update 2."
   print 'Need to clobber everything due to an IDL change in r154579 (blink)'
+  print 'Need to clobber everything due to gen file moves in r175513 (Blink)'
   if (platform() != 'ios'):
     print 'Clobber to get rid of obselete test plugin after r248358'
     print 'Clobber to rebuild GN files for V8'