src/vs/platform/protocol/electron-main/protocolMainService.ts/ProtocolMainService/handleResourceRequest
class ProtocolMainService:	private handleResourceRequest(request: Electron.ProtocolRequest, callback: ProtocolCallback): void {
		const uri = URI.parse(request.url);

		// Restore the `vscode-file` URI to a `file` URI so that we can
		// ensure the root is valid and properly tell Chrome where the
		// resource is at.
		const fileUri = FileAccess.asFileUri(uri);

		// first check by validRoots
		if (this.validRoots.findSubstr(fileUri)) {
			return callback({
				path: fileUri.fsPath
			});
		}

		// then check by validExtensions
		if (this.validExtensions.has(extname(fileUri))) {
			return callback({
				path: fileUri.fsPath
			});
		}

		// finally block to load the resource
		this.logService.error(`${Schemas.vscodeFileResource}: Refused to load resource ${fileUri.fsPath} from ${Schemas.vscodeFileResource}: protocol (original URL: ${request.url})`);

		return callback({ error: -3 /* ABORTED */ });
	}