Browser favicons: better error handling & data URL support

[kycutler]

No description provided.

[vs-code-engineering]

📬 CODENOTIFY

The following users are being notified based on files changed in this PR:

@jruales

Matched files:

• src/vs/platform/browserView/electron-main/browserView.ts

[Copilot]

Pull request overview

This PR updates the Electron-main BrowserView favicon pipeline to better handle real-world favicon sources by supporting data: URLs directly and rejecting non-image responses when fetching remote favicon URLs.

Changes:

• Treat data:image/* favicon URLs as already-resolved and return them directly.
• Validate that fetched favicon responses have an image/* content-type before converting to a data: URL.

Comments suppressed due to low confidence (1)

src/vs/platform/browserView/electron-main/browserView.ts:183

• The content-type check is case-sensitive (startsWith('image/')), but MIME types are case-insensitive. Consider lowercasing the header value (or otherwise doing a case-insensitive check) after trimming/parsing it, to avoid incorrectly rejecting valid image responses like Image/PNG.

						if (!type?.startsWith('image/')) {
							throw new Error(`Favicon is not an image: ${type}`);