Unbreak tabs.onRemove extension API in face of fast tab closure

chrome/browser/ui/tab_contents/core_tab_helper.cc

Index: chrome/browser/ui/tab_contents/core_tab_helper.cc
diff --git a/chrome/browser/ui/tab_contents/core_tab_helper.cc b/chrome/browser/ui/tab_contents/core_tab_helper.cc
index f8dc42ef7ab5af1b56897424ac89ce1f000f5b12..06492b3d21d5a857e43befbc10044a1053000bb6 100644
--- a/chrome/browser/ui/tab_contents/core_tab_helper.cc
+++ b/chrome/browser/ui/tab_contents/core_tab_helper.cc
@@ -19,7 +19,8 @@ DEFINE_WEB_CONTENTS_USER_DATA_KEY(CoreTabHelper);
 
 CoreTabHelper::CoreTabHelper(WebContents* web_contents)
     : content::WebContentsObserver(web_contents),
-      delegate_(NULL) {
+      delegate_(NULL),
+      detached_as_part_of_unload_(false) {
 }
 
 CoreTabHelper::~CoreTabHelper() {
@@ -85,6 +86,10 @@ string16 CoreTabHelper::GetStatusText() const {
   return string16();
 }
 
+bool CoreTabHelper::GetWebContentsDetachedToClose() const {
+  return detached_as_part_of_unload_;
+}
+
 void CoreTabHelper::OnCloseStarted() {
   if (close_start_time_.is_null())
     close_start_time_ = base::TimeTicks::Now();
@@ -100,6 +105,10 @@ void CoreTabHelper::OnUnloadStarted() {
   before_unload_end_time_ = base::TimeTicks::Now();
 }
 
+void CoreTabHelper::OnUnloadAboutToDetach() {
+  detached_as_part_of_unload_ = true;
+}
+
 void CoreTabHelper::OnUnloadDetachedStarted() {
   if (unload_detached_start_time_.is_null())
     unload_detached_start_time_ = base::TimeTicks::Now();