Adds tools/whitespace.txt to the list of files that trigger compile

This file is used by the cq to measure loads and other stats. We want
changes to it to result in a compile and test.

BUG=383609
TEST=none
R=iannucci@chromium.org

Review URL: https://codereview.chromium.org/403393007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284522 0039d316-1c4b-4281-b951-d872f2087c98

testing/buildbot/chromium_trybot.json

@@ -186,7 +186,8 @@
     "chrome/test/data/.*",
     "content/test/data/.*",
     "DEPS",
-    "testing/buildbot/.*"
+    "testing/buildbot/.*",
+    "tools/whitespace.txt"
   ],
 
   "filter_builders": [