Revert of [sync] Replace FakeServer's implementation with LoopbackServer invocations.

components/sync/BUILD.gn

Index: components/sync/BUILD.gn
diff --git a/components/sync/BUILD.gn b/components/sync/BUILD.gn
index 568b8a68ad42e4513f320c926268b3ace965f27b..0a8a5551e361ddd0404b1c379c167c2120d2be88 100644
--- a/components/sync/BUILD.gn
+++ b/components/sync/BUILD.gn
@@ -1024,20 +1024,30 @@
 static_library("test_support_fake_server") {
   testonly = true
   sources = [
+    "test/fake_server/bookmark_entity.cc",
+    "test/fake_server/bookmark_entity.h",
     "test/fake_server/bookmark_entity_builder.cc",
     "test/fake_server/bookmark_entity_builder.h",
     "test/fake_server/entity_builder_factory.cc",
     "test/fake_server/entity_builder_factory.h",
     "test/fake_server/fake_server.cc",
     "test/fake_server/fake_server.h",
+    "test/fake_server/fake_server_entity.cc",
+    "test/fake_server/fake_server_entity.h",
     "test/fake_server/fake_server_http_post_provider.cc",
     "test/fake_server/fake_server_http_post_provider.h",
     "test/fake_server/fake_server_network_resources.cc",
     "test/fake_server/fake_server_network_resources.h",
     "test/fake_server/fake_server_verifier.cc",
     "test/fake_server/fake_server_verifier.h",
+    "test/fake_server/permanent_entity.cc",
+    "test/fake_server/permanent_entity.h",
     "test/fake_server/sessions_hierarchy.cc",
     "test/fake_server/sessions_hierarchy.h",
+    "test/fake_server/tombstone_entity.cc",
+    "test/fake_server/tombstone_entity.h",
+    "test/fake_server/unique_client_entity.cc",
+    "test/fake_server/unique_client_entity.h",
   ]
 
   deps = [