feat(webview): incognito mode, custom user-agent, and more lifecycle events

[xaniexane]

Implements #2772 for the WebView plugin API:

• incognito create option (default true): LOAD_NO_CACHE, clears navigation history and form data on destroy.
• userAgent create option plus a setUserAgent(id, ua) runtime action (native + JS bridge).
• New lifecycle events over the message-callback channel: pageStarted, progressChanged (0-100), and loadError ({url, code, description}, main-frame only), alongside pageFinished/titleChanged.

Two honest notes:

1. I could not compile the Java in my environment (no Android SDK); the diff was reviewed line-by-line instead. Please let CI verify the build.
2. Per-instance cookie incognito is not possible on Android — CookieManager and the WebView disk cache are app-wide singletons shared with the host app WebView, so this deliberately avoids wiping them. Documented in code and in the JS API docs.

[greptile-apps]

Confidence Score: 3/5

The PR is not yet safe to merge because load failures can be delivered twice and the principal managed WebView API cannot use the newly advertised options or runtime setter.

Findings

1.  Duplicate load error events ▶
2.  Managed API omits features ▶

Summary

This PR adds WebView cache/privacy controls, creation-time and runtime user-agent overrides, and additional page lifecycle events across the Android-to-JavaScript bridge. Two integration problems remain:

• Main-frame loading failures can emit loadError twice through the modern and deprecated callback paths.
• The application-facing managed WebView API does not expose the newly implemented options or runtime user-agent setter.

Diagram

sequenceDiagram
  participant App as Managed WebView API
  participant JS as Cordova JS bridge
  participant Native as WebViewPlugin
  participant View as Android WebView
  App->>JS: create(options)
  JS->>Native: create(options)
  Native->>View: configure cache and user agent
  View-->>Native: lifecycle callbacks
  Native-->>JS: "{id, event, data}"
  JS-->>App: route event by instance ID
  App->>JS: setUserAgent(id, ua)
  JS->>Native: setUserAgent
  Native->>View: update user-agent string

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_{Reviews (1) · Last reviewed commit: "feat(webview): incognito mode, custom us..."}

[greptile-apps]

Duplicate load error events

For a main-frame load failure, this modern callback delegates to the deprecated callback, which can emit loadError when the failing URL matches view.getUrl(). The modern callback then emits the same event again, causing subscribers to process one navigation failure twice.

Knowledge Base Used:

• Plugins and platform services
• Native and external integrations