Add front_end generated to exclusive change directories

This should allow DevTools protocol rolls to no longer require
disabling this check and should also catch other CLs that make
changes to the generated source to be blocked if required.

R=jacktfranklin@chromium.org

Bug: none
Change-Id: I704ec03c7e89b2076adc4f733abf1695575035a7
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2817812
Commit-Queue: Tim van der Lippe <tvanderlippe@chromium.org>
Commit-Queue: Jack Franklin <jacktfranklin@chromium.org>
Auto-Submit: Tim van der Lippe <tvanderlippe@chromium.org>
Reviewed-by: Jack Franklin <jacktfranklin@chromium.org>
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index b75211c..d6b20d1 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -37,7 +37,7 @@
 import time
 
 EXCLUSIVE_CHANGE_DIRECTORIES = [
-    ['third_party', 'v8'],
+    ['third_party', 'v8', 'front_end/generated'],
     [
         'node_modules', 'package.json', 'package-lock.json',
         'scripts/deps/manage_node_deps.py'