Remove obsolete class DownstreamChromiumBrowserProvider.

ios/chrome/browser/BUILD.gn

 # 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.
 
 import("//build/buildflag_header.gni")
 import("//build/config/features.gni")
 import("//build/config/ios/rules.gni")
 import("//rlz/features/features.gni")
 import("//third_party/protobuf/proto_library.gni")
 
@@ skipping 239 matching lines @@
 source_set("browser_internal") {
   sources = [
     "callback_counter.h",
     "callback_counter.mm",
   ]
   deps = [
     "//base",
   ]
 }
 
-source_set("downstream_provider") {
-  sources = [
-    "downstream_chromium_browser_provider.h",
-    "downstream_chromium_browser_provider.mm",
-  ]
-  deps = [
-    ":browser",
-    "//base",
-    "//components/pref_registry",
-    "//components/prefs",
-    "//ios/chrome/browser/autofill:autofill_internal",
-    "//ios/chrome/browser/browser_state",
-    "//ios/chrome/browser/browser_state:browser_state_impl",
-    "//ios/chrome/browser/providers",
-    "//ios/chrome/browser/sync/glue",
-    "//ios/chrome/browser/sync/sessions",
-    "//ios/chrome/browser/tabs",
-    "//ios/chrome/browser/tabs:tabs_internal",
-    "//ios/chrome/browser/ui",
-    "//ios/chrome/browser/ui/webui:webui_internal",
-  ]
-}
-
-source_set("downstream_provider_factory") {
-  sources = [
-    "downstream_chromium_browser_provider_factory.mm",
-  ]
-  deps = [
-    ":downstream_provider",
-    "//base",
-    "//ios/public/provider/chrome/browser",
-  ]
-}
-
 # Clean Skeleton targets
 source_set("browser_clean_skeleton") {
   sources = [
     "browser_coordinator+internal.h",
     "browser_coordinator.h",
     "browser_coordinator.mm",
     "url_opening.h",
   ]
 
   configs += [ "//build/config/compiler:enable_arc" ]
 
   deps = [
     ":browser",
     "//base",
     "//ios/chrome/browser/browser_state",
   ]
 }