Add topic_data.get_server_history().

This isn't connected to anything yet, but you can now get
all the historical topics for a stream by calling
topic_data.get_server_history().

frontend_tests/node_tests/topic_data.js

@@ -1,5 +1,7 @@
 var topic_data = require('js/topic_data.js');
 
+set_global('channel', {});
+
 (function test_basics() {
     var stream_id = 55;
 
@@ -126,3 +128,34 @@ var topic_data = require('js/topic_data.js');
 
 
 
+(function test_server_history_end_to_end() {
+    topic_data.reset();
+
+    var stream_id = 99;
+
+    var topics = [
+        { name: 'topic3', max_id: 501 },
+        { name: 'topic2', max_id: 31 },
+        { name: 'topic1', max_id: 30 },
+    ];
+
+    var get_success_callback;
+    var on_success_called;
+
+    channel.get = function (opts) {
+        assert.equal(opts.url, '/json/users/me/99/topics');
+        assert.deepEqual(opts.data, {});
+        get_success_callback = opts.success;
+    };
+
+    topic_data.get_server_history(stream_id, function () {
+        on_success_called = true;
+    });
+
+    get_success_callback({topics: topics});
+
+    assert(on_success_called);
+
+    var history = topic_data.get_recent_names(stream_id);
+    assert.deepEqual(history, ['topic3', 'topic2', 'topic1']);
+}());

static/js/topic_data.js

@@ -156,6 +156,20 @@ exports.add_history = function (stream_id, server_history) {
     history.add_history(server_history);
 };
 
+exports.get_server_history = function (stream_id, on_success) {
+    var url = '/json/users/me/' + stream_id + '/topics';
+
+    channel.get({
+        url: url,
+        data: {},
+        success:  function (data) {
+            var server_history = data.topics;
+            exports.add_history(stream_id, server_history);
+            on_success();
+        },
+    });
+};
+
 exports.get_recent_names = function (stream_id) {
     var history = stream_dict.get(stream_id);