Add brettw's guidelines about what should be in base to base/OWNERS.

BUG=none
NOTRY=true

Review URL: https://codereview.chromium.org/686463002

Cr-Commit-Position: refs/heads/master@{#301417}

base/OWNERS

@@ -9,6 +9,19 @@ thestig@chromium.org
 # On extended leave.
 willchan@chromium.org
 
+# Chromium is a very mature project, most things that are generally useful are
+# already here, and that things not here aren't generally useful.
+#
+# Base is pulled into many projects. For example, various ChromeOS daemons. So
+# the bar for adding stuff is that it must have demonstrated wide
+# applicability. Prefer to add things closer to where they're used (i.e. "not
+# base"), and pull into base only when needed.  In a project our size,
+# sometimes even duplication is OK and inevitable.
+#
+# Adding a new logging macro DPVELOG_NE is not more clear than just
+# writing the stuff you want to log in a regular logging statement, even
+# if it makes your calling code longer. Just add it to your own code.
+
 per-file *.isolate=csharp@chromium.org
 per-file *.isolate=maruel@chromium.org
 per-file bind.h=ajwong@chromium.org