Refactor away the Browser* dependency in exclusive_access

chrome/test/base/test_browser_window.cc

Index: chrome/test/base/test_browser_window.cc
diff --git a/chrome/test/base/test_browser_window.cc b/chrome/test/base/test_browser_window.cc
index f04e7ae365f262b717860cd6d761e455db84d7f3..62f9183419bc3fdc472866a55e888d96124ca718 100644
--- a/chrome/test/base/test_browser_window.cc
+++ b/chrome/test/base/test_browser_window.cc
@@ -231,3 +231,7 @@ TestBrowserWindow::GetRenderViewHeightInsetWithDetachedBookmarkBar() {
 void TestBrowserWindow::ExecuteExtensionCommand(
     const extensions::Extension* extension,
     const extensions::Command& command) {}
+
+ExclusiveAccessContext* TestBrowserWindow::GetExclusiveAccessContext() {
+  return nullptr;
+}