Reland - 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 6bd0d7f876ec9c951dc9248ab34cd7c3debc7b46..d3402fa132cae7dd1ff7133fbdacef90301acfe5 100644
--- a/components/sync/BUILD.gn
+++ b/components/sync/BUILD.gn
@@ -1024,30 +1024,20 @@ source_set("unit_tests") {
 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 = [