Add a function to send scripts from a browsertest to an extension's background page.

chrome/chrome_tests.gypi

Index: chrome/chrome_tests.gypi
diff --git a/chrome/chrome_tests.gypi b/chrome/chrome_tests.gypi
index d85ffacc0dc75ce9f7eb1e65346346dff88d0a61..565cf71221b56cfac16cb8ac92b9ad76ff13dadc 100644
--- a/chrome/chrome_tests.gypi
+++ b/chrome/chrome_tests.gypi
@@ -214,6 +214,7 @@
         'browser/browser_keyevents_browsertest.cc',
         'browser/extensions/api/omnibox/omnibox_api_interactive_test.cc',
         'browser/extensions/api/tabs/tabs_interactive_test.cc',
+        'browser/extensions/browsertest_util.cc',
         'browser/extensions/extension_apitest.cc',
         'browser/extensions/extension_browsertest.cc',
         'browser/extensions/extension_crash_recovery_browsertest.cc',
@@ -1387,6 +1388,9 @@
         'browser/extensions/background_app_browsertest.cc',
         'browser/extensions/background_page_apitest.cc',
         'browser/extensions/background_scripts_apitest.cc',
+        'browser/extensions/browsertest_util.cc',
+        'browser/extensions/browsertest_util.h',
+        'browser/extensions/browsertest_util_browsertest.cc',
         'browser/extensions/chrome_app_api_browsertest.cc',
         'browser/extensions/content_script_apitest.cc',
         'browser/extensions/content_security_policy_apitest.cc',
@@ -2177,6 +2181,7 @@
         'app/chrome_dll_resource.h',
         'app/chrome_version.rc.version',
         'browser/extensions/api/tab_capture/tab_capture_performancetest.cc',
+        'browser/extensions/browsertest_util.cc',
         'browser/extensions/extension_apitest.cc',
         'browser/extensions/extension_browsertest.cc',
         'test/base/chrome_render_view_test.cc',