support to get a language id by filename/first line content

src/vs/editor/common/services/modeService.ts

@@ -58,7 +58,8 @@ export interface IModeService {
 	getExtensions(alias: string): string[];
 	getMimeForMode(modeId: string): string;
 	getLanguageName(modeId:string): string;
-	getModeIdForLanguageName(alias:string): string;
+	getModeIdForLanguageName(alias: string): string;
+	getModeIdByFilenameOrFirstLine(filename: string, firstLine?: string): string;
 	getModeId(commaSeparatedMimetypesOrCommaSeparatedIds: string): string;
 	getConfigurationFiles(modeId: string): string[];
 

src/vs/editor/test/common/mocks/mockModeService.ts

@@ -55,6 +55,9 @@ export class MockModeService implements IModeService {
 	getModeIdForLanguageName(alias:string): string {
 		throw new Error('Not implemented');
 	}
+	getModeIdByFilenameOrFirstLine(filename: string, firstLine?: string): string {
+		throw new Error('Not implemented');
+	}
 	getModeId(commaSeparatedMimetypesOrCommaSeparatedIds: string): string {
 		throw new Error('Not implemented');
 	}