It is possible to sometimes have a null PermissionBubbleManager.

chrome/browser/content_settings/permission_context_base.cc

Index: chrome/browser/content_settings/permission_context_base.cc
diff --git a/chrome/browser/content_settings/permission_context_base.cc b/chrome/browser/content_settings/permission_context_base.cc
index 711dbe57a09b6f0a38cca6bb4c49ef6074f62c55..e5f7a12c8f7e2797b314ff1b71f500000461ecc1 100644
--- a/chrome/browser/content_settings/permission_context_base.cc
+++ b/chrome/browser/content_settings/permission_context_base.cc
@@ -126,6 +126,8 @@ void PermissionContextBase::DecidePermission(
     PermissionBubbleManager* bubble_manager =
         PermissionBubbleManager::FromWebContents(web_contents);
     DCHECK(bubble_manager);
+    if (!bubble_manager)

[felt, 2015/03/20 14:44:17]

i think style is to have either a DCHECK or an if, but not both

[mlamouri (slow - plz ping), 2015/03/20 14:51:49]

The if is really there just to prevent the crash. We shouldn't be running into
this. The intent is to fix the sympton, if possible. The cause is clearly
somewhere else. Will add a comment.

[felt, 2015/03/20 15:00:42]

http://www.chromium.org/developers/coding-style#TOC-CHECK-DCHECK-and-NOTREACHED-

I still think you ought to remove the DCHECK, at least temporarily. Once the
underlying issue is fixed the DCHECK can be added back again.

+      return;
     scoped_ptr<PermissionBubbleRequest> request_ptr(
         new PermissionBubbleRequestImpl(
             requesting_origin, user_gesture, permission_type_,