Use standard DOM code definitions instead of custom.

This turns out to be a bit more churn than I'd hoped because ui/events/keycodes/dom/dom_code.h declares a strongly-typed enum, which can't be compared to unsigned int without a cast. Overall, I like the safety of typed enums, so I added the casts rather than declaring our own untyped equivalent, but LMK if you would prefer that.

Review URL: https://codereview.chromium.org/1403583003

Cr-Commit-Position: refs/heads/master@{#353626}
diff --git a/remoting/protocol/DEPS b/remoting/protocol/DEPS
index d0a8fc985..35a9c671 100644
--- a/remoting/protocol/DEPS
+++ b/remoting/protocol/DEPS
@@ -10,4 +10,5 @@
   "+third_party/libjingle",
   "+third_party/webrtc",
   "+third_party/protobuf/src",
+  "+ui/events/keycodes/dom",
 ]