display m.room.history_visibility updates in the timeline

src/TextForEvent.js

@@ -151,6 +151,28 @@ function textForThreePidInviteEvent(event) {
      " to join the room.";
 };
 
+function textForHistoryVisibilityEvent(event) {
+    var senderName = event.sender ? event.sender.name : event.getSender();
+    var vis = event.getContent().history_visibility;
+    var text = senderName + " made future room history visible to ";
+    if (vis === "invited") {
+        text += "all room members, from the point they are invited.";
+    }
+    else if (vis === "joined") {
+        text += "all room members, from the point they joined.";
+    }
+    else if (vis === "shared") {
+        text += "all room members.";
+    }
+    else if (vis === "world_readable") {
+        text += "anyone.";
+    }
+    else {
+        text += " unknown (" + vis + ")";
+    }
+    return text;
+};
+
 var handlers = {
     'm.room.message': textForMessageEvent,
     'm.room.name':    textForRoomNameEvent,
@@ -159,7 +181,8 @@ var handlers = {
     'm.call.invite':  textForCallInviteEvent,
     'm.call.answer':  textForCallAnswerEvent,
     'm.call.hangup':  textForCallHangupEvent,
-    'm.room.third_party_invite': textForThreePidInviteEvent
+    'm.room.third_party_invite': textForThreePidInviteEvent,
+    'm.room.history_visibility': textForHistoryVisibilityEvent,
 };
 
 module.exports = {

src/components/views/rooms/EventTile.js

@@ -44,7 +44,8 @@ var eventTileTypes = {
     'm.call.hangup' : 'messages.TextualEvent',
     'm.room.name'   : 'messages.TextualEvent',
     'm.room.topic'  : 'messages.TextualEvent',
-    'm.room.third_party_invite': 'messages.TextualEvent'
+    'm.room.third_party_invite' : 'messages.TextualEvent',
+    'm.room.history_visibility' : 'messages.TextualEvent',
 };
 
 var MAX_READ_AVATARS = 5;

src/components/views/rooms/RoomSettings.js

@@ -450,7 +450,7 @@ module.exports = React.createClass({
                             <input type="radio" id="hvis_sh" name="historyVis" value="shared"
                                     defaultChecked={historyVisibility === "shared"}
                                     onChange={this._onHistoryRadioToggle} />
-                            Members only (since the room began)
+                            Members only (since the point in time of selecting this option)
                         </label>
                         <label htmlFor="hvis_inv">
                             <input type="radio" id="hvis_inv" name="historyVis" value="invited"