Enable -Wundeclared-selector on ios.

third_party/ocmock/BUILD.gn

 # Copyright (c) 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.
 
 assert(is_mac || is_ios)
 
 config("ocmock_config") {
   include_dirs = [ "//third_party/ocmock" ]
 }
 
 config("ocmock_warnings") {
   # NSInvocation+OCMAdditions.m has some `- (void) foo; {...`
-  cflags = [ "-Wno-semicolon-before-method-body" ]
+  cflags = [
+    "-Wno-semicolon-before-method-body",
+    "-Wno-undeclared-selector",
+  ]
 }
 
 source_set("ocmock") {
   testonly = true
 
   sources = [
     # Helper for using with gtest.
     "gtest_support.h",
     "gtest_support.mm",
 
@@ skipping 46 matching lines @@
     "OCMock/OCProtocolMockObject.h",
     "OCMock/OCProtocolMockObject.m",
   ]
 
   deps = [
     "//testing/gtest",
   ]
   public_configs = [ ":ocmock_config" ]
   configs += [ ":ocmock_warnings" ]
 }