Add {Get,Set}CohortHint interface.

Export the "cohort hint" getter and setter in the client interfaces
(D-Bus and Binder). The cohort hint is sent to Omaha on every update
check request but can be ignored and/or reset by Omaha on every
response.

Other minor linter fixes to the affected files.

Bug: 31740109
Test: Build with D-Bus and with Binder.

(cherry picked from commit 5b5fa8b412312a41cfd4d7ab475b54d4f730ed2a)

Change-Id: Ieb40c2d4bbe2ce926d54b6348b22f2840d8327db
Reviewed-on: https://chromium-review.googlesource.com/395206
Commit-Ready: Alex Deymo <deymo@chromium.org>
Tested-by: Alex Deymo <deymo@chromium.org>
Reviewed-by: Christopher Book <cbook@chromium.org>
diff --git a/binder_service_brillo.cc b/binder_service_brillo.cc
index 3947ae1..5e74159 100644
--- a/binder_service_brillo.cc
+++ b/binder_service_brillo.cc
@@ -118,6 +118,22 @@
   return ret;
 }
 
+Status BinderUpdateEngineBrilloService::SetCohortHint(
+    const String16& in_cohort_hint) {
+  return CallCommonHandler(&UpdateEngineService::SetCohortHint,
+                           NormalString(in_cohort_hint));
+}
+
+Status BinderUpdateEngineBrilloService::GetCohortHint(
+    String16* out_cohort_hint) {
+  string cohort_hint;
+  auto ret =
+      CallCommonHandler(&UpdateEngineService::GetCohortHint, &cohort_hint);
+
+  *out_cohort_hint = String16(cohort_hint.c_str());
+  return ret;
+}
+
 Status BinderUpdateEngineBrilloService::SetP2PUpdatePermission(bool enabled) {
   return CallCommonHandler(&UpdateEngineService::SetP2PUpdatePermission,
                            enabled);