Android: Do not build any extensions code except for extensions_constants.

chrome/test/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 
 # GYP version: chrome/chrome_tests_unit.gypi:test_support_common
 source_set("test_support") {
+  defines = []
   testonly = true
 
   sources = [
     "base/chrome_process_util.cc",
     "base/chrome_process_util.h",
     "base/chrome_process_util_mac.cc",
     "base/chrome_render_view_host_test_harness.cc",
     "base/chrome_render_view_host_test_harness.h",
     "base/chrome_test_launcher.cc",
     "base/chrome_test_launcher.h",
@@ skipping 82 matching lines @@
     "//sql:test_support",
     "//sync",
     "//testing/gmock",
     "//testing/gtest",
     "//third_party/zlib",
     "//ui/message_center:test_support",
   ]
 
   if (!is_ios) {
     deps += [
-      "//chrome/common/extensions/api",
       "//chrome/plugin",
       "//chrome/renderer",
       "//chrome/utility",
       "//content/public/child",
       "//content/public/common",
       "//content/public/plugin",
       "//content/public/renderer",
       "//content/public/utility",
       "//components/autofill/core/browser:test_support",
       "//components/captive_portal:test_support",
       "//components/infobars/core",
       "//components/sessions:test_support",
-      "//extensions:test_support",
       "//google_apis:test_support",
       "//ipc:test_support",
       "//media:test_support",
       "//ppapi:ppapi_shared",
       "//sql:test_support",
       "//third_party/leveldatabase",
       "//ui/base",
       "//ui/events:events_base",
       "//ui/gl",
     ]
@@ skipping 21 matching lines @@
       "ppapi/ppapi_test.h",
     ]
   }
 
   if (use_ash) {
     deps += [ "//ash:test_support" ]
   }
   if (toolkit_views) {
     deps += [ "//ui/views:test_support" ]
   }
+
+  if (enable_background) {
+    defines += [ "ENABLE_BACKGROUND=1" ]
+  }
+
+  if (enable_extensions) {
+    deps += [
+      "//chrome/common/extensions/api",
+      "//extensions:test_support",
+    ]
+  }
 }
 
 source_set("test_support_unit") {
   testonly = true
   sources = [
     "../browser/sync/glue/session_sync_test_helper.cc",
     "../browser/sync/glue/session_sync_test_helper.h",
     "base/run_all_unittests.cc",
   ]
 
   deps = [
     ":test_support",
     "//base",
     "//chrome:resources",
     "//chrome:strings",
     "//chrome/browser",
     "//chrome/common",
     "//mojo/edk/system",
     "//mojo/environment:chromium",
   ]
 }