Workaround for a crashing appcache bug seen on the crash servers

webkit/appcache/appcache_storage_impl.cc

 // Copyright (c) 2012 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 "webkit/appcache/appcache_storage_impl.h"
 
 #include <algorithm>
 #include <functional>
 #include <set>
 #include <vector>
@@ skipping 406 matching lines @@
 
 void AppCacheStorageImpl::StoreOrLoadTask::CreateCacheAndGroupFromRecords(
     scoped_refptr<AppCache>* cache, scoped_refptr<AppCacheGroup>* group) {
   DCHECK(storage_ && cache && group);
 
   (*cache) = storage_->working_set_.GetCache(cache_record_.cache_id);
   if (cache->get()) {
     (*group) = cache->get()->owning_group();
     DCHECK(group->get());
     DCHECK_EQ(group_record_.group_id, group->get()->group_id());
+
+    // TODO(michaeln): histogram is fishing for clues to crbug/95101
+    if (!cache->get()->GetEntry(group_record_.manifest_url)) {
+      AppCacheHistograms::AddMissingManifestDetectedAtCallsite(
+          AppCacheHistograms::CALLSITE_0);
+    }
+
     storage_->NotifyStorageAccessed(group_record_.origin);
     return;
   }
 
   (*cache) = new AppCache(storage_->service_, cache_record_.cache_id);
   cache->get()->InitializeWithDatabaseRecords(
       cache_record_, entry_records_,
       intercept_namespace_records_,
       fallback_namespace_records_,
       online_whitelist_records_);
   cache->get()->set_complete(true);
 
   (*group) = storage_->working_set_.GetGroup(group_record_.manifest_url);
   if (group->get()) {
     DCHECK(group_record_.group_id == group->get()->group_id());
     group->get()->AddCache(cache->get());
+
+    // TODO(michaeln): histogram is fishing for clues to crbug/95101
+    if (!cache->get()->GetEntry(group_record_.manifest_url)) {
+      AppCacheHistograms::AddMissingManifestDetectedAtCallsite(
+          AppCacheHistograms::CALLSITE_1);
+    }
   } else {
     (*group) = new AppCacheGroup(
         storage_->service_, group_record_.manifest_url,
         group_record_.group_id);
     group->get()->set_creation_time(group_record_.creation_time);
     group->get()->AddCache(cache->get());
+
+    // TODO(michaeln): histogram is fishing for clues to crbug/95101
+    if (!cache->get()->GetEntry(group_record_.manifest_url)) {
+      AppCacheHistograms::AddMissingManifestDetectedAtCallsite(
+          AppCacheHistograms::CALLSITE_2);
+    }
   }
   DCHECK(group->get()->newest_complete_cache() == cache->get());
 
   // We have to update foriegn entries if MarkEntryAsForeignTasks
   // are in flight.
   std::vector<GURL> urls;
   storage_->GetPendingForeignMarkingsForCache(cache->get()->cache_id(), &urls);
   for (std::vector<GURL>::iterator iter = urls.begin();
        iter != urls.end(); ++iter) {
     DCHECK(cache->get()->GetEntry(*iter));
@@ skipping 957 matching lines @@
   // TODO(michaeln): distinguish between a simple update of an existing
   // cache that just adds new master entry(s), and the insertion of a
   // whole new cache. The StoreGroupAndCacheTask as written will handle
   // the simple update case in a very heavy weight way (delete all and
   // the reinsert all over again).
   DCHECK(group && delegate && newest_cache);
   scoped_refptr<StoreGroupAndCacheTask> task(
       new StoreGroupAndCacheTask(this, group, newest_cache));
   task->AddDelegate(GetOrCreateDelegateReference(delegate));
   task->GetQuotaThenSchedule();
+
+  // TODO(michaeln): histogram is fishing for clues to crbug/95101
+  if (!newest_cache->GetEntry(group->manifest_url())) {
+    AppCacheHistograms::AddMissingManifestDetectedAtCallsite(
+        AppCacheHistograms::CALLSITE_3);
+  }
 }
 
 void AppCacheStorageImpl::FindResponseForMainRequest(
     const GURL& url, const GURL& preferred_manifest_url,
     Delegate* delegate) {
   DCHECK(delegate);
 
   const GURL* url_ptr = &url;
   GURL url_no_ref;
   if (url.has_ref()) {
@@ skipping 352 matching lines @@
     Disable();
     if (!is_incognito_) {
       VLOG(1) << "Deleting existing appcache data and starting over.";
       db_thread_->PostTask(
           FROM_HERE, base::Bind(&DeleteDirectory, cache_directory_));
     }
   }
 }
 
 }  // namespace appcache