Remove public/features.gni

Now that Oilpan is shipped, we no longer need public/features.gni.

BUG=

Review-Url: https://codereview.chromium.org/2320343002
Cr-Commit-Position: refs/heads/master@{#417501}

third_party/WebKit/Source/config.gni

@@ -3,7 +3,6 @@
 # found in the LICENSE file.
 
 import("//build/config/ui.gni")
-import("//third_party/WebKit/public/features.gni")
 
 if (is_android) {
   import("//build/config/android/config.gni")

third_party/WebKit/public/features.gni

-# Copyright 2015 The Chromium Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-
-declare_args() {
-  # Enables the Oilpan garbage-collection infrastructure.
-  enable_oilpan = true
-}