Revert of [cast_channel] Move cast_channel related files from //extensions to //components

extensions/BUILD.gn

 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//extensions/features/features.gni")
 import("//testing/test.gni")
 import("//tools/grit/grit_rule.gni")
 import("//tools/grit/repack.gni")
 
 assert(enable_extensions)
 
@@ skipping 42 matching lines @@
   deps = [
     "//device/serial:serial_mojo__generator",
     "//extensions/common:mojo__generator",
     "//extensions/common/api:mojom__generator",
   ]
 }
 
 static_library("test_support") {
   testonly = true
   sources = [
+    "browser/api/cast_channel/cast_test_util.cc",
+    "browser/api/cast_channel/cast_test_util.h",
     "browser/api/declarative/test_rules_registry.cc",
     "browser/api/declarative/test_rules_registry.h",
     "browser/api/dns/mock_host_resolver_creator.cc",
     "browser/api/dns/mock_host_resolver_creator.h",
     "browser/api/storage/settings_test_util.cc",
     "browser/api/storage/settings_test_util.h",
     "browser/api_test_utils.cc",
     "browser/api_test_utils.h",
     "browser/api_unittest.cc",
     "browser/api_unittest.h",
@@ skipping 51 matching lines @@
     "test/test_permission_message_provider.h",
   ]
 
   # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
   configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 
   deps = [
     ":extensions_resources",
     "//base",
     "//components/cast_certificate:test_support",
-    "//components/cast_channel:test_support",
     "//components/guest_view/browser:test_support",
     "//components/prefs:test_support",
     "//components/sync_preferences:test_support",
     "//content/public/common",
     "//content/test:test_support",
     "//extensions/browser",
     "//extensions/browser/api:api_registration",
     "//extensions/common",
     "//extensions/common/api",
     "//extensions/test:extensions_features",
     "//net:test_support",
     "//testing/gmock",
     "//testing/gtest",
     "//third_party/cld",
   ]
 
   public_deps = [
     "//content/public/browser",
+    "//extensions/common/api/cast_channel:cast_channel_proto",
   ]
 }
 
 repack("shell_and_test_pak") {
   sources = [
     "$root_gen_dir/blink/public/resources/blink_image_resources_100_percent.pak",
     "$root_gen_dir/blink/public/resources/blink_resources.pak",
     "$root_gen_dir/content/app/strings/content_strings_en-US.pak",
     "$root_gen_dir/content/browser/devtools/devtools_resources.pak",
     "$root_gen_dir/content/content_resources.pak",
@@ skipping 190 matching lines @@
     "//testing/gtest",
     "//third_party/hunspell",
     "//third_party/icu",
     "//third_party/libpng",
     "//third_party/zlib",
     "//ui/base:test_support",
     "//ui/resources:ui_test_pak",
     "//ui/web_dialogs:test_support",
   ]
 }