[Clean up] Move VariationsHttpHeaderProvider into a subdirectory.

components/suggestions/BUILD.gn

 # Copyright 2014 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.
 
 static_library("suggestions") {
   sources = [
     "blacklist_store.cc",
     "blacklist_store.h",
     "image_encoder.h",
     "image_fetcher.h",
     "image_fetcher_delegate.h",
     "image_manager.cc",
     "image_manager.h",
     "suggestions_pref_names.cc",
     "suggestions_pref_names.h",
     "suggestions_service.cc",
     "suggestions_service.h",
     "suggestions_store.cc",
     "suggestions_store.h",
     "suggestions_utils.cc",
     "suggestions_utils.h",
   ]
 
   deps = [
     "//base",
     "//components/keyed_service/core",
     "//components/pref_registry",
     "//components/suggestions/proto",
     "//components/variations",
+    "//components/variations/net",
     "//net",
     "//ui/gfx",
     "//url",
   ]
 
   if (is_ios) {
     sources += [
       "image_encoder_ios.mm",
     ]
   } else {
     sources += [
       "image_encoder.cc",
     ]
   }
 }