webrtc/base: add dependent setting for gtest include directory that was missed when creating base_tests.gyp. Same as https://code.google.com/p/webrtc/source/browse/trunk/talk/libjingle_tests.gyp?r=6484#39

BUG=N/A
R=wu@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/16799004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6574 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/base/base_tests.gyp b/webrtc/base/base_tests.gyp
index c5cc7b8..ca0d72a 100644
--- a/webrtc/base/base_tests.gyp
+++ b/webrtc/base/base_tests.gyp
@@ -29,6 +29,9 @@
         'base.gyp:webrtc_base',
         '<(DEPTH)/testing/gtest.gyp:gtest',
       ],
+      'export_dependent_settings': [
+        '<(DEPTH)/testing/gtest.gyp:gtest',
+      ],
     },
     {
       'target_name': 'webrtc_base_tests',