Make SpellCheckPanel compiled and used only on Mac

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("//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",
     "spellcheck.h",
     "spellcheck_language.cc",
     "spellcheck_language.h",
     "spellcheck_panel.cc",
     "spellcheck_panel.h",
     "spellcheck_provider.cc",
     "spellcheck_provider.h",
     "spellcheck_worditerator.cc",
     "spellcheck_worditerator.h",
     "spelling_engine.h",
   ]
 
+  # TODO(xiaochengh): Negate these checks so that each file is listed only once.
   if (!use_browser_spellchecker) {
     sources -= [
       "platform_spelling_engine.cc",
       "platform_spelling_engine.h",
     ]
   }
 
+  if (!has_spellcheck_panel) {
+    sources -= [
+      "spellcheck_panel.cc",
+      "spellcheck_panel.h",
+    ]
+  }
+
   if (is_android) {
     sources -= [
       "hunspell_engine.cc",
       "hunspell_engine.h",
     ]
   }
 
   public_deps = [
     "//components/spellcheck:build_features",
   ]
@@ skipping 59 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)
   }
 }