Make extensions/browser/api/* sources to publicly depend on //ipc

extensions/browser/api/test/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("test") {
   sources = [
     "test_api.cc",
     "test_api.h",
   ]
 
   deps = [
     "//content/public/common",
     "//extensions/common/api",
   ]
+
+  public_deps = [
+    "//extensions/browser:browser_sources",
+  ]
 }