Null checks to prevent occasional crash

chrome/browser/ui/browser_list.cc

Index: chrome/browser/ui/browser_list.cc
diff --git a/chrome/browser/ui/browser_list.cc b/chrome/browser/ui/browser_list.cc
index 851a9f8ca791e33639009faadca239dc3ef2017c..4cf87982070641ec8d2345976920197a278086dd 100644
--- a/chrome/browser/ui/browser_list.cc
+++ b/chrome/browser/ui/browser_list.cc
@@ -151,6 +151,9 @@ void BrowserList::TryToCloseBrowserList(const BrowserVector& browsers_to_close,
     const base::FilePath& profile_path) {
   for (BrowserVector::const_iterator it = browsers_to_close.begin();
        it != browsers_to_close.end(); ++it) {
+    // TODO(mlerman): crbug.com/423229, if we can determine why window() is
+    // false we can better solve the underlying issue here.
+    DCHECK((*it)->window());

[Peter Kasting, 2014/10/30 03:07:50]

I would change these two DCHECKs to CHECKs if you're trying to diagnose an
issue, since most users don't have DCHECKs on.

Plus, CHECKs obviate the need for a conditional -- you will either pass the
CHECK or crash.

We can then take action fairly quickly in response to a CHECK, so we don't have
huge numbers of users hitting it.

     if ((*it)->CallBeforeUnloadHandlers(
             base::Bind(&BrowserList::PostBeforeUnloadHandlers,
                        browsers_to_close,
@@ -163,8 +166,12 @@ void BrowserList::TryToCloseBrowserList(const BrowserVector& browsers_to_close,
   on_close_success.Run(profile_path);
 
   for (BrowserVector::const_iterator it = browsers_to_close.begin();
-       it != browsers_to_close.end(); ++it)
-    (*it)->window()->Close();
+       it != browsers_to_close.end(); ++it) {
+    // TODO(mlerman): If reproducible, determine cause if window() being null.
+    DCHECK((*it)->window());
+    if ((*it)->window())
+      (*it)->window()->Close();
+  }
 }
 
 // static