Move ImageFetcher to its own target.

ios/chrome/browser/net/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.
 
 source_set("net") {
   sources = [
     "chrome_cookie_store_ios_client.h",
     "chrome_cookie_store_ios_client.mm",
     "connection_type_observer_bridge.h",
     "connection_type_observer_bridge.mm",
@@ skipping 18 matching lines @@
     "net_types.h",
     "proxy_service_factory.cc",
     "proxy_service_factory.h",
     "retryable_url_fetcher.h",
     "retryable_url_fetcher.mm",
   ]
   deps = [
     "//base",
     "//components/component_updater",
     "//components/content_settings/core/browser",
+    "//components/image_fetcher/ios",
     "//components/pref_registry",
     "//components/prefs",
     "//components/proxy_config",
     "//components/update_client",
     "//ios/chrome/browser",
     "//ios/chrome/browser/browser_state",
     "//ios/chrome/browser/browsing_data",
-    "//ios/chrome/browser/webp_transcode",
     "//ios/net",
     "//ios/web",
     "//net",
     "//net:extras",
     "//url",
   ]
   allow_circular_includes_from = [
     "//ios/chrome/browser",
     "//ios/chrome/browser/browser_state",
   ]
 }
 
 source_set("test_support") {
   testonly = true
   sources = [
     "mock_image_fetcher.h",
     "mock_image_fetcher.mm",
   ]
   deps = [
     ":net",
     "//testing/gmock",
   ]
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
     "cookie_util_unittest.mm",
-    "image_fetcher_unittest.mm",
     "metrics_network_client_unittest.mm",
     "retryable_url_fetcher_unittest.mm",
   ]
   deps = [
     ":net",
     "//base",
     "//base/test:test_support",
     "//ios/web:test_support",
     "//net",
     "//net:test_support",
     "//testing/gtest",
   ]
 }