src/vs/workbench/api/common/extHostWebviewView.ts/ExtHostWebviewViews/getWebviewView
class ExtHostWebviewViews:	private getWebviewView(handle: string): ExtHostWebviewView {
		const entry = this._webviewViews.get(handle);
		if (!entry) {
			throw new Error('No webview found');
		}
		return entry;
	}