Fix the leaking memory test in NativeWidgetAuraTest.PreventFocusOnNonActivableWindow.
Fix the leaking memory test in NativeWidgetAuraTest.PreventFocusOnNonActivableWindow.

BUG=515594

Review URL: https://codereview.chromium.org/1787933002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#380808}

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