[Extensions] Move Feature channel code into //extensions

extensions/common/features/complex_feature.cc

Index: extensions/common/features/complex_feature.cc
diff --git a/extensions/common/features/complex_feature.cc b/extensions/common/features/complex_feature.cc
index 9a330c1ff64166e83d4c752d8086c518d9549253..5f041dbbc982786192cf3db7d81f36cc041dcbc5 100644
--- a/extensions/common/features/complex_feature.cc
+++ b/extensions/common/features/complex_feature.cc
@@ -102,16 +102,4 @@ bool ComplexFeature::IsInternal() const {
   return features_[0]->IsInternal();
 }
 
-std::string ComplexFeature::GetAvailabilityMessage(AvailabilityResult result,
-                                                   Manifest::Type type,
-                                                   const GURL& url,
-                                                   Context context) const {
-  if (result == IS_AVAILABLE)
-    return std::string();
-
-  // TODO(justinlin): Form some kind of combined availabilities/messages from
-  // SimpleFeatures.
-  return features_[0]->GetAvailabilityMessage(result, type, url, context);
-}
-
 }  // namespace extensions