Update chromium's DEPS-file presubmits with new 'Str' type.

And remove //buildtools/checkdeps/ specific OWNERS file.

Bug: 1102536
Change-Id: I6a12f0be226655ab37ada23548b6e5a172b27f8b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2283411
Reviewed-by: Dirk Pranke <dpranke@google.com>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#785522}
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index 5b02cddc..2c11665 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -2354,6 +2354,7 @@
   local_scope = {}
   global_scope = {
       'Var': _VarImpl(local_scope).Lookup,
+      'Str': str,
   }
   exec contents in global_scope, local_scope
   return local_scope