add Init Script
Installs a script that runs before any page script runs on current and future documents.
Throws
ErrorCode.UNSUPPORTED if the device's WebView package lacks the WebViewFeature.DOCUMENT_START_SCRIPT feature.
Installs a script that runs before any page script runs on current and future documents.
ErrorCode.UNSUPPORTED if the device's WebView package lacks the WebViewFeature.DOCUMENT_START_SCRIPT feature.