Force Mac Views for HostedAppOpaqueBrowserFrameViewTest on mac-cocoa-rel

This CL makes HostedAppOpaqueBrowserFrameViewTest force enable Mac Views
to fix a crash on mac-cocoa-rel.

Bug: 885164
Change-Id: I8cd754954c9119a65c8aca94b7a07f2159e3f95d
Reviewed-on: https://chromium-review.googlesource.com/1237733Reviewed-by: Trent Apted <tapted@chromium.org>
Commit-Queue: Alan Cutter <alancutter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593073}

chrome/browser/ui/views/frame/opaque_browser_frame_view_browsertest.cc

@@ -13,6 +13,7 @@
 #include "chrome/common/chrome_features.h"
 #include "chrome/common/web_application_info.h"
 #include "chrome/test/base/in_process_browser_test.h"
+#include "chrome/test/views/scoped_macviews_browser_mode.h"
 
 // Tests hosted app windows that use the OpaqueBrowserFrameView implementation
 // for their non client frames.
@@ -64,6 +65,8 @@ class HostedAppOpaqueBrowserFrameViewTest : public InProcessBrowserTest {
   HostedAppButtonContainer* hosted_app_button_container_ = nullptr;
 
  private:
+  test::ScopedMacViewsBrowserMode force_mac_views_{true};
+
   DISALLOW_COPY_AND_ASSIGN(HostedAppOpaqueBrowserFrameViewTest);
 };