Refine //extensions DEPS on //ui

extensions/DEPS

Index: extensions/DEPS
diff --git a/extensions/DEPS b/extensions/DEPS
index d2bbec8b4697b7e0649188db6c6eb6d960f140a1..21a0ba611c5d533047bc5b923395944c0e57b349 100644
--- a/extensions/DEPS
+++ b/extensions/DEPS
@@ -13,7 +13,16 @@ include_rules = [
   "+grit/extensions_resources.h",
   "+mojo/public",
   "+testing",
-  "+ui",
+
+  # Minimal UI dependencies. There are two good rules for UI dependencies here:
+  #
+  #   1) UI components should only be added as they are needed, and
+  #   2) if //content doesn't allow it, //extensions probably won't allow it.
+  #      (see for example ui/views)
+  "-ui",
+  "+ui/base",
+  "+ui/gfx",
+  "+ui/events",
 
   # NOTE: Please do not add includes without talking to the app shell team;
   # see OWNERS for this directory.