add comment why sync state should be scoped

Author: sandy081

src/vs/workbench/services/environment/browser/environmentService.ts

@@ -114,6 +114,11 @@ export class BrowserWorkbenchEnvironmentService implements IWorkbenchEnvironment
 	@memoize
 	get snippetsHome(): URI { return joinPath(this.userRoamingDataHome, 'snippets'); }
 
+	/*
+	 * In Web every workspace can potentially have scoped user-data and/or extensions and if Sync state is shared then it can make
+	 * Sync error prone - say removing extensions from another workspace. Hence scope Sync state per workspace.
+	 * Sync scoped to a workspace is capable of handling even if workspaces/windows share same user data and extensions.
+	 */
 	@memoize
 	get userDataSyncHome(): URI { return joinPath(this.userRoamingDataHome, 'sync', this.options.workspaceId); }