Convert spellcheck to a buildflag header.

components/spellcheck/renderer/BUILD.gn

 # Copyright 2016 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.
 
-import("//build/config/features.gni")
+import("//components/spellcheck/spellcheck_build_features.gni")
 
 source_set("renderer") {
   sources = [
     "custom_dictionary_engine.cc",
     "custom_dictionary_engine.h",
     "hunspell_engine.cc",
     "hunspell_engine.h",
     "platform_spelling_engine.cc",
     "platform_spelling_engine.h",
     "spellcheck.cc",
@@ skipping 14 matching lines @@
     ]
   }
 
   if (is_android) {
     sources -= [
       "hunspell_engine.cc",
       "hunspell_engine.h",
     ]
   }
 
+  public_deps = [
+    "//components/spellcheck:build_features",
+  ]
   deps = [
     "//base:i18n",
     "//components/spellcheck/common",
     "//content/public/renderer",
     "//ipc",
     "//third_party/WebKit/public:blink",
     "//third_party/icu",
   ]
 
   if (!is_android) {
@@ skipping 48 matching lines @@
   ]
 
   if (is_mac && !is_ios) {
     deps += [ "//third_party/hunspell" ]
   }
 
   if (is_win) {
     cflags = [ "/wd4267" ]  # conversion from 'size_t' to 'int' on x64 (crbug.com/633312)
   }
 }