Revert of Remove void** from disk_cache interface. (patchset crosswalk-project#30 id:650001 of https://codereview.chromium.org/542733002/)

Reason for revert:
Introduced memory leaks on linux asan
http://build.chromium.org/p/chromium.memory/builders/Linux%20ASan%20LSan%20Tests%20%281%29/builds/5892:
Direct leak of 80 byte(s) in 2 object(s) allocated from:
#0 0x501ccb in operator new(unsigned long) (/b/build/slave/Linux_ASan_LSan_Tests__1_/build/src/out/Release/net_unittests+0x501ccb)
#1 0x309f8d7 in disk_cache::BackendImpl::OpenNextEntryImpl(void**) net/disk_cache/blockfile/backend_impl.cc:620:5
#2 0x30a02cd in disk_cache::BackendImpl::SyncOpenNextEntry(void**, disk_cache::Entry**) net/disk_cache/blockfile/backend_impl.cc:436:17
#3 0x30d49dd in disk_cache::BackendIO::ExecuteBackendOperation() net/disk_cache/blockfile/in_flight_backend_io.cc:248:17
#4 0x2e3b0bf in Run base/callback.h:401:12
crosswalk-project#5 0x2e3b0bf in base::debug::TaskAnnotator::RunTask(char const*, char const*, base::PendingTask const&) base/debug/task_annotator.cc:62
crosswalk-project#6 0x2dc22fc in base::MessageLoop::RunTask(base::PendingTask const&) base/message_loop/message_loop.cc:446:3
crosswalk-project#7 0x2dc33cc in DeferOrRunPendingTask base/message_loop/message_loop.cc:456:5
crosswalk-project#8 0x2dc33cc in base::MessageLoop::DoWork() base/message_loop/message_loop.cc:565
crosswalk-project#9 0x2e2361f in base::MessagePumpLibevent::Run(base::MessagePump::Delegate*) base/message_loop/message_pump_libevent.cc:232:21
crosswalk-project#10 0x2ddd94b in base::RunLoop::Run() base/run_loop.cc:54:3
crosswalk-project#11 0x2dc0bc4 in base::MessageLoop::Run() base/message_loop/message_loop.cc:308:3
crosswalk-project#12 0x2e0ad90 in base::Thread::ThreadMain() base/threading/thread.cc:228:5
crosswalk-project#13 0x2dfeaf0 in base::(anonymous namespace)::ThreadFunc(void*) base/threading/platform_thread_posix.cc:80:3
crosswalk-project#14 0x7fa9f4e0ce99 in start_thread /build/buildd/eglibc-2.15/nptl/pthread_create.c:308

Indirect leak of 64 byte(s) in 2 object(s) allocated from:
#0 0x501ccb in operator new(unsigned long) (/b/build/slave/Linux_ASan_LSan_Tests__1_/build/src/out/Release/net_unittests+0x501ccb)
#1 0x30ebaaf in disk_cache::Rankings::GetNext(disk_cache::StorageBlock<disk_cache::RankingsNode>*, disk_cache::Rankings::List) net/disk_cache/blockfile/rankings.cc:435:5
#2 0x30a219d in disk_cache::BackendImpl::OpenFollowingEntryFromList(disk_cache::Rankings::List, disk_cache::StorageBlock<disk_cache::RankingsNode>**, disk_cache::EntryImpl**) net/disk_cache/blockfile/backend_impl.cc:1694:36
#3 0x309fa3d in disk_cache::BackendImpl::OpenNextEntryImpl(void**) net/disk_cache/blockfile/backend_impl.cc:638:11
#4 0x30a02cd in disk_cache::BackendImpl::SyncOpenNextEntry(void**, disk_cache::Entry**) net/disk_cache/blockfile/backend_impl.cc:436:17
crosswalk-project#5 0x30d49dd in disk_cache::BackendIO::ExecuteBackendOperation() net/disk_cache/blockfile/in_flight_backend_io.cc:248:17
crosswalk-project#6 0x2e3b0bf in Run base/callback.h:401:12
crosswalk-project#7 0x2e3b0bf in base::debug::TaskAnnotator::RunTask(char const*, char const*, base::PendingTask const&) base/debug/task_annotator.cc:62
crosswalk-project#8 0x2dc22fc in base::MessageLoop::RunTask(base::PendingTask const&) base/message_loop/message_loop.cc:446:3
crosswalk-project#9 0x2dc33cc in DeferOrRunPendingTask base/message_loop/message_loop.cc:456:5
crosswalk-project#10 0x2dc33cc in base::MessageLoop::DoWork() base/message_loop/message_loop.cc:565
crosswalk-project#11 0x2e2361f in base::MessagePumpLibevent::Run(base::MessagePump::Delegate*) base/message_loop/message_pump_libevent.cc:232:21
crosswalk-project#12 0x2ddd94b in base::RunLoop::Run() base/run_loop.cc:54:3
crosswalk-project#13 0x2dc0bc4 in base::MessageLoop::Run() base/message_loop/message_loop.cc:308:3
crosswalk-project#14 0x2e0ad90 in base::Thread::ThreadMain() base/threading/thread.cc:228:5
crosswalk-project#15 0x2dfeaf0 in base::(anonymous namespace)::ThreadFunc(void*) base/threading/platform_thread_posix.cc:80:3
crosswalk-project#16 0x7fa9f4e0ce99 in start_thread /build/buildd/eglibc-2.15/nptl/pthread_create.c:308

Indirect leak of 36 byte(s) in 1 object(s) allocated from:
#0 0x501ccb in operator new(unsigned long) (/b/build/slave/Linux_ASan_LSan_Tests__1_/build/src/out/Release/net_unittests+0x501ccb)
#1 0x30c0696 in AllocateData net/disk_cache/blockfile/storage_block-inl.h:179:5
#2 0x30c0696 in disk_cache::StorageBlock<disk_cache::RankingsNode>::Load() net/disk_cache/blockfile/storage_block-inl.h:121
#3 0x30e6fe9 in disk_cache::Rankings::GetRanking(disk_cache::StorageBlock<disk_cache::RankingsNode>*) net/disk_cache/blockfile/rankings.cc:586:8
#4 0x30ebd5a in disk_cache::Rankings::GetNext(disk_cache::StorageBlock<disk_cache::RankingsNode>*, disk_cache::Rankings::List) net/disk_cache/blockfile/rankings.cc:440:8
crosswalk-project#5 0x30a219d in disk_cache::BackendImpl::OpenFollowingEntryFromList(disk_cache::Rankings::List, disk_cache::StorageBlock<disk_cache::RankingsNode>**, disk_cache::EntryImpl**) net/disk_cache/blockfile/backend_impl.cc:1694:36
crosswalk-project#6 0x309fa3d in disk_cache::BackendImpl::OpenNextEntryImpl(void**) net/disk_cache/blockfile/backend_impl.cc:638:11
crosswalk-project#7 0x30a02cd in disk_cache::BackendImpl::SyncOpenNextEntry(void**, disk_cache::Entry**) net/disk_cache/blockfile/backend_impl.cc:436:17
crosswalk-project#8 0x30d49dd in disk_cache::BackendIO::ExecuteBackendOperation() net/disk_cache/blockfile/in_flight_backend_io.cc:248:17
crosswalk-project#9 0x2e3b0bf in Run base/callback.h:401:12
crosswalk-project#10 0x2e3b0bf in base::debug::TaskAnnotator::RunTask(char const*, char const*, base::PendingTask const&) base/debug/task_annotator.cc:62
crosswalk-project#11 0x2dc22fc in base::MessageLoop::RunTask(base::PendingTask const&) base/message_loop/message_loop.cc:446:3
crosswalk-project#12 0x2dc33cc in DeferOrRunPendingTask base/message_loop/message_loop.cc:456:5
crosswalk-project#13 0x2dc33cc in base::MessageLoop::DoWork() base/message_loop/message_loop.cc:565
crosswalk-project#14 0x2e2361f in base::MessagePumpLibevent::Run(base::MessagePump::Delegate*) base/message_loop/message_pump_libevent.cc:232:21
crosswalk-project#15 0x2ddd94b in base::RunLoop::Run() base/run_loop.cc:54:3
crosswalk-project#16 0x2dc0bc4 in base::MessageLoop::Run() base/message_loop/message_loop.cc:308:3
crosswalk-project#17 0x2e0ad90 in base::Thread::ThreadMain() base/threading/thread.cc:228:5
crosswalk-project#18 0x2dfeaf0 in base::(anonymous namespace)::ThreadFunc(void*) base/threading/platform_thread_posix.cc:80:3
crosswalk-project#19 0x7fa9f4e0ce99 in start_thread /build/buildd/eglibc-2.15/nptl/pthread_create.c:308

Original issue's description:
> Remove void** from disk_cache interface.
>
> Enumeration and iteration were passing around void**. With this CL, we
> instead use an Iterator object.
>
> [email protected],[email protected],[email protected]
> BUG=413644
>
> Committed: https://crrev.com/732c8306d4864296511e7a3a252724b1bb34c342
> Cr-Commit-Position: refs/heads/master@{#295659}

[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected]
NOTREECHECKS=true
NOTRY=true
BUG=413644

Review URL: https://codereview.chromium.org/585833002

Cr-Commit-Position: refs/heads/master@{#295677}

Author: vasilii

content/browser/gpu/shader_disk_cache.cc

@@ -95,7 +95,7 @@ class ShaderDiskReadHelper
 
   base::WeakPtr<ShaderDiskCache> cache_;
   OpType op_type_;
-  scoped_ptr<disk_cache::Backend::Iterator> iter_;
+  void* iter_;
   scoped_refptr<net::IOBufferWithSize> buf_;
   int host_id_;
   disk_cache::Entry* entry_;
@@ -243,6 +243,7 @@ ShaderDiskReadHelper::ShaderDiskReadHelper(
     int host_id)
     : cache_(cache),
       op_type_(OPEN_NEXT),
+      iter_(NULL),
       buf_(NULL),
       host_id_(host_id),
       entry_(NULL) {
@@ -290,10 +291,10 @@ int ShaderDiskReadHelper::OpenNextEntry() {
   DCHECK(CalledOnValidThread());
   // Called through OnOpComplete, so we know |cache_| is valid.
   op_type_ = OPEN_NEXT_COMPLETE;
-  if (!iter_)
-    iter_ = cache_->backend()->CreateIterator();
-  return iter_->OpenNextEntry(
-      &entry_, base::Bind(&ShaderDiskReadHelper::OnOpComplete, this));
+  return cache_->backend()->OpenNextEntry(
+      &iter_,
+      &entry_,
+      base::Bind(&ShaderDiskReadHelper::OnOpComplete, this));
 }
 
 int ShaderDiskReadHelper::OpenNextEntryComplete(int rv) {
@@ -338,7 +339,8 @@ int ShaderDiskReadHelper::ReadComplete(int rv) {
 int ShaderDiskReadHelper::IterationComplete(int rv) {
   DCHECK(CalledOnValidThread());
   // Called through OnOpComplete, so we know |cache_| is valid.
-  iter_.reset();
+  cache_->backend()->EndEnumeration(&iter_);
+  iter_ = NULL;
   op_type_ = TERMINATE;
   return net::OK;
 }

content/browser/service_worker/service_worker_cache.cc

@@ -597,13 +597,16 @@ struct ServiceWorkerCache::KeysContext {
       : original_callback(callback),
         cache(cache),
         out_keys(new ServiceWorkerCache::Requests()),
+        backend_iterator(NULL),
         enumerated_entry(NULL) {}
 
   ~KeysContext() {
     for (size_t i = 0, max = entries.size(); i < max; ++i)
       entries[i]->Close();
     if (enumerated_entry)
       enumerated_entry->Close();
+    if (cache && backend_iterator && cache->backend_)
+      cache->backend_->EndEnumeration(&backend_iterator);
   }
 
   // The callback passed to the Keys() function.
@@ -619,7 +622,7 @@ struct ServiceWorkerCache::KeysContext {
   scoped_ptr<ServiceWorkerCache::Requests> out_keys;
 
   // Used for enumerating cache entries.
-  scoped_ptr<disk_cache::Backend::Iterator> backend_iterator;
+  void* backend_iterator;
   disk_cache::Entry* enumerated_entry;
 };
 
@@ -771,14 +774,14 @@ void ServiceWorkerCache::Keys(const RequestsCallback& callback) {
   scoped_ptr<KeysContext> keys_context(
       new KeysContext(callback, weak_ptr_factory_.GetWeakPtr()));
 
-  keys_context->backend_iterator = backend_->CreateIterator();
-  disk_cache::Backend::Iterator& iterator = *keys_context->backend_iterator;
+  void** backend_iterator = &keys_context->backend_iterator;
   disk_cache::Entry** enumerated_entry = &keys_context->enumerated_entry;
 
   net::CompletionCallback open_entry_callback =
       base::Bind(KeysDidOpenNextEntry, base::Passed(keys_context.Pass()));
 
-  int rv = iterator.OpenNextEntry(enumerated_entry, open_entry_callback);
+  int rv = backend_->OpenNextEntry(
+      backend_iterator, enumerated_entry, open_entry_callback);
 
   if (rv != net::ERR_IO_PENDING)
     open_entry_callback.Run(rv);
@@ -861,12 +864,14 @@ void ServiceWorkerCache::KeysDidOpenNextEntry(
   keys_context->enumerated_entry = NULL;
 
   // Enumerate the next entry.
-  disk_cache::Backend::Iterator& iterator = *keys_context->backend_iterator;
+  void** backend_iterator = &keys_context->backend_iterator;
   disk_cache::Entry** enumerated_entry = &keys_context->enumerated_entry;
+
   net::CompletionCallback open_entry_callback =
       base::Bind(KeysDidOpenNextEntry, base::Passed(keys_context.Pass()));
 
-  rv = iterator.OpenNextEntry(enumerated_entry, open_entry_callback);
+  rv = cache->backend_->OpenNextEntry(
+      backend_iterator, enumerated_entry, open_entry_callback);
 
   if (rv != net::ERR_IO_PENDING)
     open_entry_callback.Run(rv);