Keep chat stickied to the bottom on resize

Fixes the chat not staying at the bottom when opening the on-screen keyboard on mobile.

client/js/libs/jquery/stickyscroll.js

@@ -1,29 +1,48 @@
 (function($) {
 	$.fn.unsticky = function() {
-		return this.unbind(".sticky");
+		return this.trigger("unstick.sticky").unbind(".sticky");
 	};
 
 	$.fn.sticky = function() {
 		var self = this;
 		var stuckToBottom = true;
+		var lastStick = 0;
 
-		self
+		var keepToBottom = function() {
-			.on("scroll.sticky", function(e) {
-				stuckToBottom = self.isScrollBottom();
-			})
-			.on("msg.sticky", function() {
 			if (stuckToBottom) {
 				self.scrollBottom();
 			}
+		};
+
+		$(window).on("resize.sticky", keepToBottom);
+		self
+			.on("unstick.sticky", function() {
+				$(window).off("resize.sticky", keepToBottom);
 			})
+			.on("scroll.sticky", function() {
+				// When resizing, sometimes the browser sends a bunch of extra scroll events due to content
+				// reflow, so if we resized within 250ms we can assume it's one of those. The order of said
+				// events is not predictable, and scroll can happen last, so not setting stuckToBottom is
+				// not enough, we have to force the scroll still.
+				if (stuckToBottom && Date.now() - lastStick < 250) {
+					self.scrollBottom();
+				} else {
+					stuckToBottom = self.isScrollBottom();
+				}
+			})
+			.on("scrollBottom.sticky", function() {
+				stuckToBottom = true;
+				lastStick = Date.now();
+				this.scrollTop = this.scrollHeight;
+			})
+			.on("msg.sticky", keepToBottom)
 			.scrollBottom();
 
 		return self;
 	};
 
 	$.fn.scrollBottom = function() {
-		var el = this[0];
+		this.trigger("scrollBottom.sticky");
-		this.scrollTop(el.scrollHeight);
 		return this;
 	};