update doc

src/vs/vscode.proposed.d.ts

@@ -1100,12 +1100,20 @@ declare module 'vscode' {
 
 	export namespace window {
 
-		export function registerUserDataSyncProvider(name: string, userDataProvider: UserDataSyncProvider): Disposable;
+		/**
+		 * Register an [UserDataSyncProvider](#UserDataSyncProvider) to read and write user data.
+		 * @param name Name of the user data sync provider
+		 * @param userDataSyncProvider [UserDataSyncProvider](#UserDataSyncProvider) to read and write user data
+		 */
+		export function registerUserDataSyncProvider(name: string, userDataSyncProvider: UserDataSyncProvider): Disposable;
 
 	}
 
 	export class UserDataError extends Error {
 
+		/**
+		 * Create an error to signal that writing user data with given ref is rejected, becase of new ref.
+		 */
 		static Rejected(): FileSystemError;
 
 		/**
@@ -1114,10 +1122,29 @@ declare module 'vscode' {
 		constructor();
 	}
 
+	/**
+	 * User data sync provider to read and write user data.
+	 */
 	export interface UserDataSyncProvider {
 
+		/**
+		 * Reads the content and its ref for the given key.
+		 * Return <code>null</code> if key does not exists.
+		 *
+		 * @param key key of the content to read
+		 * @returns the content and its ref for the given key. Return <code>null</code> if key does not exists.
+		 */
 		read(key: string): Promise<{ content: string, ref: string } | null>;
 
+		/**
+		 * Writes the new content based on the given ref for the given key.
+		 *
+		 * @param key key of the content to write
+		 * @param content new content to write
+		 * @param ref ref of the content on which the content to write is based on
+		 * @throws [Rejected](#UserDataError.Rejected) if the ref is not the latest.
+		 * @returns the latest ref of the content.
+		 */
 		write(key: string, content: string, ref: string | null): Promise<string>;
 
 	}