Allow trivial BUILD.gn changes to content/browser/BULID.gn.

Reduce thrash on content/browser/OWNERS and content/renderer/OWNERS for
trivial adds/deletes from the BUILD.gn file. All of content/OWNERS,
chrome/browser/OWNERS, and chrome/renderer/OWNERS already has this, so
there is precedent.

BUG=869232

Change-Id: I535294fd904da1739fa7abb95ce18da162eb42bb
Reviewed-on: https://chromium-review.googlesource.com/1150815
Commit-Queue: Yuri Wiitala <miu@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579272}

content/browser/OWNERS

 # For Android
 boliu@chromium.org
 
+# These are for the common case of adding or renaming files. If you're doing
+# structural changes, please get a review from a reviewer in this file.
+per-file BUILD.gn=*
+
 # For security review.
 per-file child_process_security_policy_impl.*=set noparent
 per-file child_process_security_policy_impl.*=creis@chromium.org

content/renderer/OWNERS

 haraken@chromium.org
 
+# These are for the common case of adding or renaming files. If you're doing
+# structural changes, please get a review from a reviewer in this file.
+per-file BUILD.gn=*
+
 # Mac Sandbox profiles.
 per-file *.sb=set noparent
 per-file *.sb=rsesek@chromium.org