Fix browser tests on Mac

headless/test/headless_browser_test.cc

Index: headless/test/headless_browser_test.cc
diff --git a/headless/test/headless_browser_test.cc b/headless/test/headless_browser_test.cc
index 44e3f9b5d7d9b482ece969d46a8d24fc09f38dcf..a5191a3ccae26e9834cff332d7c04ec4be4806a3 100644
--- a/headless/test/headless_browser_test.cc
+++ b/headless/test/headless_browser_test.cc
@@ -5,8 +5,10 @@
 #include "headless/test/headless_browser_test.h"
 
 #include "base/files/file_path.h"
+#include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/message_loop/message_loop.h"
+#include "base/path_service.h"
 #include "base/run_loop.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/render_process_host.h"
@@ -121,6 +123,14 @@ void LoadObserver::OnResponseReceived(
 }
 
 HeadlessBrowserTest::HeadlessBrowserTest() {
+#if defined(OS_MACOSX)
+  // On Mac the source root is not set properly. We override it by assuming
+  // that is two directories up from the execution test file.
+  base::FilePath dir_exe_path;
+  CHECK(PathService::Get(base::DIR_EXE, &dir_exe_path));
+  dir_exe_path = dir_exe_path.Append("../../");
+  CHECK(PathService::Override(base::DIR_SOURCE_ROOT, dir_exe_path));
+#endif  // defined(OS_MACOSX)
   base::FilePath headless_test_data(FILE_PATH_LITERAL("headless/test/data"));
   CreateTestServer(headless_test_data);
 }