src/vs/workbench/api/common/extHostSearch.ts/ExtHostSearch/registerTextSearchProvider
class ExtHostSearch:	registerTextSearchProvider(scheme: string, provider: vscode.TextSearchProvider): IDisposable {
		if (this._textSearchUsedSchemes.has(scheme)) {
			throw new Error(`a text search provider for the scheme '${scheme}' is already registered`);
		}

		this._textSearchUsedSchemes.add(scheme);
		const handle = this._handlePool++;
		this._textSearchProvider.set(handle, provider);
		this._proxy.$registerTextSearchProvider(handle, this._transformScheme(scheme));
		return toDisposable(() => {
			this._textSearchUsedSchemes.delete(scheme);
			this._textSearchProvider.delete(handle);
			this._proxy.$unregisterProvider(handle);
		});
	}