[webview] fix missing properties on events when contextIsolation: true

Editor assessment

The subject carries real information, events were missing properties when contextIsolation is true in a webview, but the style is sloppy: a bracketed [webview] tag substitutes for a proper scope, and the verb is doubled (fix ... fix missing properties). The fix type is right, and the condition clause is genuinely useful. No body exists to explain the mechanism, whether property copying was skipped under isolation, and no footers appear. Hygiene suffers from the bracket-prefix habit and redundancy. Understandable, but the presentation is unpolished and the rationale unstated.