src/vs/workbench/contrib/debug/browser/debugSession.ts/DebugSession/loadSource
class DebugSession:	loadSource(resource: URI): Promise<DebugProtocol.SourceResponse | undefined> {
		if (!this.raw) {
			return Promise.reject(new Error(localize('noDebugAdapter', "No debugger available, can not send '{0}'", 'loadSource')));
		}

		const source = this.getSourceForUri(resource);
		let rawSource: DebugProtocol.Source;
		if (source) {
			rawSource = source.raw;
		} else {
			// create a Source
			const data = Source.getEncodedDebugData(resource);
			rawSource = { path: data.path, sourceReference: data.sourceReference };
		}

		return this.raw.source({ sourceReference: rawSource.sourceReference || 0, source: rawSource });
	}