From 290f5877b95585e73c6ac1b73b11d8df39b724cd Mon Sep 17 00:00:00 2001
From: Stephen Blott
Date: Tue, 5 May 2015 07:32:36 +0100
Subject: Guard against missing sender.

When a tab is closing, Chrome sometimes doesn't set sender.tab.  To
reproduce, navigate (by entering the URLs directly) between www.bing.com
and www.google.com.

Fixes #1630.  Partially.  We still have a space leak.
---
 background_scripts/main.coffee | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

(limited to 'background_scripts')

diff --git a/background_scripts/main.coffee b/background_scripts/main.coffee
index 37c65592..103cc61e 100644
--- a/background_scripts/main.coffee
+++ b/background_scripts/main.coffee
@@ -385,7 +385,8 @@ setIcon = (request, sender) ->
   chrome.browserAction.setIcon tabId: sender.tab.id, path: path
 
 handleUpdateScrollPosition = (request, sender) ->
-  updateScrollPosition(sender.tab, request.scrollX, request.scrollY)
+  # See note re. sender.tab at unregisterFrame.
+  updateScrollPosition sender.tab, request.scrollX, request.scrollY if sender.tab?
 
 updateScrollPosition = (tab, scrollX, scrollY) ->
   tabInfoMap[tab.id].scrollX = scrollX
@@ -598,8 +599,11 @@ registerFrame = (request, sender) ->
   (frameIdsForTab[sender.tab.id] ?= []).push request.frameId
 
 unregisterFrame = (request, sender) ->
-  tabId = sender.tab.id
-  if frameIdsForTab[tabId]?
+  # When a tab is closing, Chrome sometimes passes on messages without sender.tab.  Therefore, we guard
+  # against this.
+  # FIXME(smblott) Consequently, we have a space leak in frameIdsForTab, tabInfoMap and urlForTab.
+  tabId = sender.tab?.id
+  if tabId? and frameIdsForTab[tabId]?
     if request.tab_is_closing
       updateOpenTabs sender.tab, true
     else
-- 
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