Mac Support for drag-and-drop tests that start dragging via mouse simulation.

content/public/test/browser_test_utils.cc

Index: content/public/test/browser_test_utils.cc
diff --git a/content/public/test/browser_test_utils.cc b/content/public/test/browser_test_utils.cc
index 06394e01ddbe1c70b8bbfce8ed459b507e7326bc..a69ea176be0890ca473dd1219b881ba06692caa4 100644
--- a/content/public/test/browser_test_utils.cc
+++ b/content/public/test/browser_test_utils.cc
@@ -1857,4 +1857,9 @@ void PwnMessageHelper::FileSystemWrite(RenderProcessHost* process,
     waiter.WaitForEndUpdate();
 }
 
+void RegisterDragStartCallback(DragStartCallback callback) {
+  RenderWidgetHostImpl::RegisterDragStartCallbackForTesting(
+      std::move(callback));
+}
+
 }  // namespace content