It is possible to sometimes have a null PermissionBubbleManager.

chrome/browser/content_settings/permission_context_base.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/content_settings/permission_context_base.h"
 
 #include "base/logging.h"
 #include "base/prefs/pref_service.h"
 #include "chrome/browser/content_settings/permission_bubble_request_impl.h"
 #include "chrome/browser/content_settings/permission_context_uma_util.h"
@@ skipping 108 matching lines @@
 
   PermissionContextUmaUtil::PermissionRequested(
       permission_type_, requesting_origin);
 
   if (PermissionBubbleManager::Enabled()) {
     if (pending_bubbles_.get(id.ToString()) != NULL)
       return;
     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_,
             profile_->GetPrefs()->GetString(prefs::kAcceptLanguages),
             base::Bind(&PermissionContextBase::PermissionDecided,
                        weak_factory_.GetWeakPtr(), id, requesting_origin,
                        embedding_origin, callback),
             base::Bind(&PermissionContextBase::CleanUpBubble,
                        weak_factory_.GetWeakPtr(), id)));
     PermissionBubbleRequest* request = request_ptr.get();
@@ skipping 92 matching lines @@
   DCHECK_EQ(requesting_origin, requesting_origin.GetOrigin());
   DCHECK_EQ(embedding_origin, embedding_origin.GetOrigin());
   DCHECK(content_setting == CONTENT_SETTING_ALLOW ||
          content_setting == CONTENT_SETTING_BLOCK);
 
   profile_->GetHostContentSettingsMap()->SetContentSetting(
       ContentSettingsPattern::FromURLNoWildcard(requesting_origin),
       ContentSettingsPattern::FromURLNoWildcard(embedding_origin),
       permission_type_, std::string(), content_setting);
 }