Add m-esr52 at 52.6.0

1 files changed, 1486 insertions, 0 deletions

diff --git a/dom/storage/DOMStorageDBThread.cpp b/dom/storage/DOMStorageDBThread.cpp
new file mode 100644
index 000000000..183be5c5c
--- /dev/null
+++ b/dom/storage/DOMStorageDBThread.cpp
@@ -0,0 +1,1486 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "DOMStorageDBThread.h"
+#include "DOMStorageDBUpdater.h"
+#include "DOMStorageCache.h"
+#include "DOMStorageManager.h"
+
+#include "nsIEffectiveTLDService.h"
+#include "nsDirectoryServiceUtils.h"
+#include "nsAppDirectoryServiceDefs.h"
+#include "nsThreadUtils.h"
+#include "nsProxyRelease.h"
+#include "mozStorageCID.h"
+#include "mozStorageHelper.h"
+#include "mozIStorageService.h"
+#include "mozIStorageBindingParamsArray.h"
+#include "mozIStorageBindingParams.h"
+#include "mozIStorageValueArray.h"
+#include "mozIStorageFunction.h"
+#include "mozilla/BasePrincipal.h"
+#include "nsIObserverService.h"
+#include "nsVariant.h"
+#include "mozilla/IOInterposer.h"
+#include "mozilla/Services.h"
+#include "mozilla/Tokenizer.h"
+
+// How long we collect write oprerations
+// before they are flushed to the database
+// In milliseconds.
+#define FLUSHING_INTERVAL_MS 5000
+
+// Write Ahead Log's maximum size is 512KB
+#define MAX_WAL_SIZE_BYTES 512 * 1024
+
+// Current version of the database schema
+#define CURRENT_SCHEMA_VERSION 1
+
+namespace mozilla {
+namespace dom {
+
+namespace { // anon
+
+// This is only a compatibility code for schema version 0.  Returns the 'scope' key
+// in the schema version 0 format for the scope column.
+nsCString
+Scheme0Scope(DOMStorageCacheBridge* aCache)
+{
+  nsCString result;
+
+  nsCString suffix = aCache->OriginSuffix();
+
+  PrincipalOriginAttributes oa;
+  if (!suffix.IsEmpty()) {
+    DebugOnly<bool> success = oa.PopulateFromSuffix(suffix);
+    MOZ_ASSERT(success);
+  }
+
+  if (oa.mAppId != nsIScriptSecurityManager::NO_APP_ID || oa.mInIsolatedMozBrowser) {
+    result.AppendInt(oa.mAppId);
+    result.Append(':');
+    result.Append(oa.mInIsolatedMozBrowser ? 't' : 'f');
+    result.Append(':');
+  }
+
+  // If there is more than just appid and/or inbrowser stored in origin
+  // attributes, put it to the schema 0 scope as well.  We must do that
+  // to keep the scope column unique (same resolution as schema 1 has
+  // with originAttributes and originKey columns) so that switch between
+  // schema 1 and 0 always works in both ways.
+  nsAutoCString remaining;
+  oa.mAppId = 0;
+  oa.mInIsolatedMozBrowser = false;
+  oa.CreateSuffix(remaining);
+  if (!remaining.IsEmpty()) {
+    MOZ_ASSERT(!suffix.IsEmpty());
+
+    if (result.IsEmpty()) {
+      // Must contain the old prefix, otherwise we won't search for the whole
+      // origin attributes suffix.
+      result.Append(NS_LITERAL_CSTRING("0:f:"));
+    }
+    // Append the whole origin attributes suffix despite we have already stored
+    // appid and inbrowser.  We are only looking for it when the scope string
+    // starts with "$appid:$inbrowser:" (with whatever valid values).
+    //
+    // The OriginAttributes suffix is a string in a form like:
+    // "^addonId=101&userContextId=5" and it's ensured it always starts with '^'
+    // and never contains ':'.  See OriginAttributes::CreateSuffix.
+    result.Append(suffix);
+    result.Append(':');
+  }
+
+  result.Append(aCache->OriginNoSuffix());
+
+  return result;
+}
+
+} // anon
+
+
+DOMStorageDBBridge::DOMStorageDBBridge()
+{
+}
+
+
+DOMStorageDBThread::DOMStorageDBThread()
+: mThread(nullptr)
+, mThreadObserver(new ThreadObserver())
+, mStopIOThread(false)
+, mWALModeEnabled(false)
+, mDBReady(false)
+, mStatus(NS_OK)
+, mWorkerStatements(mWorkerConnection)
+, mReaderStatements(mReaderConnection)
+, mDirtyEpoch(0)
+, mFlushImmediately(false)
+, mPriorityCounter(0)
+{
+}
+
+nsresult
+DOMStorageDBThread::Init()
+{
+  nsresult rv;
+
+  // Need to determine location on the main thread, since
+  // NS_GetSpecialDirectory access the atom table that can
+  // be accessed only on the main thread.
+  rv = NS_GetSpecialDirectory(NS_APP_USER_PROFILE_50_DIR,
+                              getter_AddRefs(mDatabaseFile));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = mDatabaseFile->Append(NS_LITERAL_STRING("webappsstore.sqlite"));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Ensure mozIStorageService init on the main thread first.
+  nsCOMPtr<mozIStorageService> service =
+    do_GetService(MOZ_STORAGE_SERVICE_CONTRACTID, &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Need to keep the lock to avoid setting mThread later then
+  // the thread body executes.
+  MonitorAutoLock monitor(mThreadObserver->GetMonitor());
+
+  mThread = PR_CreateThread(PR_USER_THREAD, &DOMStorageDBThread::ThreadFunc, this,
+                            PR_PRIORITY_LOW, PR_GLOBAL_THREAD, PR_JOINABLE_THREAD,
+                            262144);
+  if (!mThread) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
+  return NS_OK;
+}
+
+nsresult
+DOMStorageDBThread::Shutdown()
+{
+  if (!mThread) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+
+  Telemetry::AutoTimer<Telemetry::LOCALDOMSTORAGE_SHUTDOWN_DATABASE_MS> timer;
+
+  {
+    MonitorAutoLock monitor(mThreadObserver->GetMonitor());
+
+    // After we stop, no other operations can be accepted
+    mFlushImmediately = true;
+    mStopIOThread = true;
+    monitor.Notify();
+  }
+
+  PR_JoinThread(mThread);
+  mThread = nullptr;
+
+  return mStatus;
+}
+
+void
+DOMStorageDBThread::SyncPreload(DOMStorageCacheBridge* aCache, bool aForceSync)
+{
+  PROFILER_LABEL_FUNC(js::ProfileEntry::Category::STORAGE);
+  if (!aForceSync && aCache->LoadedCount()) {
+    // Preload already started for this cache, just wait for it to finish.
+    // LoadWait will exit after LoadDone on the cache has been called.
+    SetHigherPriority();
+    aCache->LoadWait();
+    SetDefaultPriority();
+    return;
+  }
+
+  // Bypass sync load when an update is pending in the queue to write, we would
+  // get incosistent data in the cache.  Also don't allow sync main-thread preload
+  // when DB open and init is still pending on the background thread.
+  if (mDBReady && mWALModeEnabled) {
+    bool pendingTasks;
+    {
+      MonitorAutoLock monitor(mThreadObserver->GetMonitor());
+      pendingTasks = mPendingTasks.IsOriginUpdatePending(aCache->OriginSuffix(), aCache->OriginNoSuffix()) ||
+                     mPendingTasks.IsOriginClearPending(aCache->OriginSuffix(), aCache->OriginNoSuffix());
+    }
+
+    if (!pendingTasks) {
+      // WAL is enabled, thus do the load synchronously on the main thread.
+      DBOperation preload(DBOperation::opPreload, aCache);
+      preload.PerformAndFinalize(this);
+      return;
+    }
+  }
+
+  // Need to go asynchronously since WAL is not allowed or scheduled updates
+  // need to be flushed first.
+  // Schedule preload for this cache as the first operation.
+  nsresult rv = InsertDBOp(new DBOperation(DBOperation::opPreloadUrgent, aCache));
+
+  // LoadWait exits after LoadDone of the cache has been called.
+  if (NS_SUCCEEDED(rv)) {
+    aCache->LoadWait();
+  }
+}
+
+void
+DOMStorageDBThread::AsyncFlush()
+{
+  MonitorAutoLock monitor(mThreadObserver->GetMonitor());
+  mFlushImmediately = true;
+  monitor.Notify();
+}
+
+bool
+DOMStorageDBThread::ShouldPreloadOrigin(const nsACString& aOrigin)
+{
+  MonitorAutoLock monitor(mThreadObserver->GetMonitor());
+  return mOriginsHavingData.Contains(aOrigin);
+}
+
+void
+DOMStorageDBThread::GetOriginsHavingData(InfallibleTArray<nsCString>* aOrigins)
+{
+  MonitorAutoLock monitor(mThreadObserver->GetMonitor());
+  for (auto iter = mOriginsHavingData.Iter(); !iter.Done(); iter.Next()) {
+    aOrigins->AppendElement(iter.Get()->GetKey());
+  }
+}
+
+nsresult
+DOMStorageDBThread::InsertDBOp(DOMStorageDBThread::DBOperation* aOperation)
+{
+  MonitorAutoLock monitor(mThreadObserver->GetMonitor());
+
+  // Sentinel to don't forget to delete the operation when we exit early.
+  nsAutoPtr<DOMStorageDBThread::DBOperation> opScope(aOperation);
+
+  if (NS_FAILED(mStatus)) {
+    MonitorAutoUnlock unlock(mThreadObserver->GetMonitor());
+    aOperation->Finalize(mStatus);
+    return mStatus;
+  }
+
+  if (mStopIOThread) {
+    // Thread use after shutdown demanded.
+    MOZ_ASSERT(false);
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+
+  switch (aOperation->Type()) {
+  case DBOperation::opPreload:
+  case DBOperation::opPreloadUrgent:
+    if (mPendingTasks.IsOriginUpdatePending(aOperation->OriginSuffix(), aOperation->OriginNoSuffix())) {
+      // If there is a pending update operation for the scope first do the flush
+      // before we preload the cache.  This may happen in an extremely rare case
+      // when a child process throws away its cache before flush on the parent
+      // has finished.  If we would preloaded the cache as a priority operation 
+      // before the pending flush, we would have got an inconsistent cache content.
+      mFlushImmediately = true;
+    } else if (mPendingTasks.IsOriginClearPending(aOperation->OriginSuffix(), aOperation->OriginNoSuffix())) {
+      // The scope is scheduled to be cleared, so just quickly load as empty.
+      // We need to do this to prevent load of the DB data before the scope has
+      // actually been cleared from the database.  Preloads are processed
+      // immediately before update and clear operations on the database that
+      // are flushed periodically in batches.
+      MonitorAutoUnlock unlock(mThreadObserver->GetMonitor());
+      aOperation->Finalize(NS_OK);
+      return NS_OK;
+    }
+    MOZ_FALLTHROUGH;
+
+  case DBOperation::opGetUsage:
+    if (aOperation->Type() == DBOperation::opPreloadUrgent) {
+      SetHigherPriority(); // Dropped back after urgent preload execution
+      mPreloads.InsertElementAt(0, aOperation);
+    } else {
+      mPreloads.AppendElement(aOperation);
+    }
+
+    // DB operation adopted, don't delete it.
+    opScope.forget();
+
+    // Immediately start executing this.
+    monitor.Notify();
+    break;
+
+  default:
+    // Update operations are first collected, coalesced and then flushed
+    // after a short time.
+    mPendingTasks.Add(aOperation);
+
+    // DB operation adopted, don't delete it.
+    opScope.forget();
+
+    ScheduleFlush();
+    break;
+  }
+
+  return NS_OK;
+}
+
+void
+DOMStorageDBThread::SetHigherPriority()
+{
+  ++mPriorityCounter;
+  PR_SetThreadPriority(mThread, PR_PRIORITY_URGENT);
+}
+
+void
+DOMStorageDBThread::SetDefaultPriority()
+{
+  if (--mPriorityCounter <= 0) {
+    PR_SetThreadPriority(mThread, PR_PRIORITY_LOW);
+  }
+}
+
+void
+DOMStorageDBThread::ThreadFunc(void* aArg)
+{
+  PR_SetCurrentThreadName("localStorage DB");
+  mozilla::IOInterposer::RegisterCurrentThread();
+
+  DOMStorageDBThread* thread = static_cast<DOMStorageDBThread*>(aArg);
+  thread->ThreadFunc();
+  mozilla::IOInterposer::UnregisterCurrentThread();
+}
+
+void
+DOMStorageDBThread::ThreadFunc()
+{
+  nsresult rv = InitDatabase();
+
+  MonitorAutoLock lockMonitor(mThreadObserver->GetMonitor());
+
+  if (NS_FAILED(rv)) {
+    mStatus = rv;
+    mStopIOThread = true;
+    return;
+  }
+
+  // Create an nsIThread for the current PRThread, so we can observe runnables
+  // dispatched to it.
+  nsCOMPtr<nsIThread> thread = NS_GetCurrentThread();
+  nsCOMPtr<nsIThreadInternal> threadInternal = do_QueryInterface(thread);
+  MOZ_ASSERT(threadInternal); // Should always succeed.
+  threadInternal->SetObserver(mThreadObserver);
+
+  while (MOZ_LIKELY(!mStopIOThread || mPreloads.Length() ||
+                    mPendingTasks.HasTasks() ||
+                    mThreadObserver->HasPendingEvents())) {
+    // Process xpcom events first.
+    while (MOZ_UNLIKELY(mThreadObserver->HasPendingEvents())) {
+      mThreadObserver->ClearPendingEvents();
+      MonitorAutoUnlock unlock(mThreadObserver->GetMonitor());
+      bool processedEvent;
+      do {
+        rv = thread->ProcessNextEvent(false, &processedEvent);
+      } while (NS_SUCCEEDED(rv) && processedEvent);
+    }
+
+    if (MOZ_UNLIKELY(TimeUntilFlush() == 0)) {
+      // Flush time is up or flush has been forced, do it now.
+      UnscheduleFlush();
+      if (mPendingTasks.Prepare()) {
+        {
+          MonitorAutoUnlock unlockMonitor(mThreadObserver->GetMonitor());
+          rv = mPendingTasks.Execute(this);
+        }
+
+        if (!mPendingTasks.Finalize(rv)) {
+          mStatus = rv;
+          NS_WARNING("localStorage DB access broken");
+        }
+      }
+      NotifyFlushCompletion();
+    } else if (MOZ_LIKELY(mPreloads.Length())) {
+      nsAutoPtr<DBOperation> op(mPreloads[0]);
+      mPreloads.RemoveElementAt(0);
+      {
+        MonitorAutoUnlock unlockMonitor(mThreadObserver->GetMonitor());
+        op->PerformAndFinalize(this);
+      }
+
+      if (op->Type() == DBOperation::opPreloadUrgent) {
+        SetDefaultPriority(); // urgent preload unscheduled
+      }
+    } else if (MOZ_UNLIKELY(!mStopIOThread)) {
+      lockMonitor.Wait(TimeUntilFlush());
+    }
+  } // thread loop
+
+  mStatus = ShutdownDatabase();
+
+  if (threadInternal) {
+    threadInternal->SetObserver(nullptr);
+  }
+}
+
+
+NS_IMPL_ISUPPORTS(DOMStorageDBThread::ThreadObserver, nsIThreadObserver)
+
+NS_IMETHODIMP
+DOMStorageDBThread::ThreadObserver::OnDispatchedEvent(nsIThreadInternal *thread)
+{
+  MonitorAutoLock lock(mMonitor);
+  mHasPendingEvents = true;
+  lock.Notify();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DOMStorageDBThread::ThreadObserver::OnProcessNextEvent(nsIThreadInternal *thread,
+                                       bool mayWait)
+{
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DOMStorageDBThread::ThreadObserver::AfterProcessNextEvent(nsIThreadInternal *thread,
+                                          bool eventWasProcessed)
+{
+  return NS_OK;
+}
+
+
+extern void
+ReverseString(const nsCSubstring& aSource, nsCSubstring& aResult);
+
+nsresult
+DOMStorageDBThread::OpenDatabaseConnection()
+{
+  nsresult rv;
+
+  MOZ_ASSERT(!NS_IsMainThread());
+
+  nsCOMPtr<mozIStorageService> service
+      = do_GetService(MOZ_STORAGE_SERVICE_CONTRACTID, &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = service->OpenUnsharedDatabase(mDatabaseFile, getter_AddRefs(mWorkerConnection));
+  if (rv == NS_ERROR_FILE_CORRUPTED) {
+    // delete the db and try opening again
+    rv = mDatabaseFile->Remove(false);
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = service->OpenUnsharedDatabase(mDatabaseFile, getter_AddRefs(mWorkerConnection));
+  }
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return NS_OK;
+}
+
+nsresult
+DOMStorageDBThread::OpenAndUpdateDatabase()
+{
+  nsresult rv;
+
+  // Here we are on the worker thread. This opens the worker connection.
+  MOZ_ASSERT(!NS_IsMainThread());
+
+  rv = OpenDatabaseConnection();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = TryJournalMode();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return NS_OK;
+}
+
+nsresult
+DOMStorageDBThread::InitDatabase()
+{
+  nsresult rv;
+
+  // Here we are on the worker thread. This opens the worker connection.
+  MOZ_ASSERT(!NS_IsMainThread());
+
+  rv = OpenAndUpdateDatabase();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = DOMStorageDBUpdater::Update(mWorkerConnection);
+  if (NS_FAILED(rv)) {
+    // Update has failed, rather throw the database away and try
+    // opening and setting it up again.
+    rv = mWorkerConnection->Close();
+    mWorkerConnection = nullptr;
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    rv = mDatabaseFile->Remove(false);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    rv = OpenAndUpdateDatabase();
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  // Create a read-only clone
+  (void)mWorkerConnection->Clone(true, getter_AddRefs(mReaderConnection));
+  NS_ENSURE_TRUE(mReaderConnection, NS_ERROR_FAILURE);
+
+  // Database open and all initiation operation are done.  Switching this flag
+  // to true allow main thread to read directly from the database.
+  // If we would allow this sooner, we would have opened a window where main thread
+  // read might operate on a totaly broken and incosistent database.
+  mDBReady = true;
+
+  // List scopes having any stored data
+  nsCOMPtr<mozIStorageStatement> stmt;
+  // Note: result of this select must match DOMStorageManager::CreateOrigin()
+  rv = mWorkerConnection->CreateStatement(NS_LITERAL_CSTRING(
+        "SELECT DISTINCT originAttributes || ':' || originKey FROM webappsstore2"),
+        getter_AddRefs(stmt));
+  NS_ENSURE_SUCCESS(rv, rv);
+  mozStorageStatementScoper scope(stmt);
+
+  bool exists;
+  while (NS_SUCCEEDED(rv = stmt->ExecuteStep(&exists)) && exists) {
+    nsAutoCString foundOrigin;
+    rv = stmt->GetUTF8String(0, foundOrigin);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    MonitorAutoLock monitor(mThreadObserver->GetMonitor());
+    mOriginsHavingData.PutEntry(foundOrigin);
+  }
+
+  return NS_OK;
+}
+
+nsresult
+DOMStorageDBThread::SetJournalMode(bool aIsWal)
+{
+  nsresult rv;
+
+  nsAutoCString stmtString(
+    MOZ_STORAGE_UNIQUIFY_QUERY_STR "PRAGMA journal_mode = ");
+  if (aIsWal) {
+    stmtString.AppendLiteral("wal");
+  } else {
+    stmtString.AppendLiteral("truncate");
+  }
+
+  nsCOMPtr<mozIStorageStatement> stmt;
+  rv = mWorkerConnection->CreateStatement(stmtString, getter_AddRefs(stmt));
+  NS_ENSURE_SUCCESS(rv, rv);
+  mozStorageStatementScoper scope(stmt);
+
+  bool hasResult = false;
+  rv = stmt->ExecuteStep(&hasResult);
+  NS_ENSURE_SUCCESS(rv, rv);
+  if (!hasResult) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsAutoCString journalMode;
+  rv = stmt->GetUTF8String(0, journalMode);
+  NS_ENSURE_SUCCESS(rv, rv);
+  if ((aIsWal && !journalMode.EqualsLiteral("wal")) ||
+      (!aIsWal && !journalMode.EqualsLiteral("truncate"))) {
+    return NS_ERROR_FAILURE;
+  }
+
+  return NS_OK;
+}
+
+nsresult
+DOMStorageDBThread::TryJournalMode()
+{
+  nsresult rv;
+
+  rv = SetJournalMode(true);
+  if (NS_FAILED(rv)) {
+    mWALModeEnabled = false;
+
+    rv = SetJournalMode(false);
+    NS_ENSURE_SUCCESS(rv, rv);
+  } else {
+    mWALModeEnabled = true;
+
+    rv = ConfigureWALBehavior();
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  return NS_OK;
+}
+
+nsresult
+DOMStorageDBThread::ConfigureWALBehavior()
+{
+  // Get the DB's page size
+  nsCOMPtr<mozIStorageStatement> stmt;
+  nsresult rv = mWorkerConnection->CreateStatement(NS_LITERAL_CSTRING(
+    MOZ_STORAGE_UNIQUIFY_QUERY_STR "PRAGMA page_size"
+  ), getter_AddRefs(stmt));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  bool hasResult = false;
+  rv = stmt->ExecuteStep(&hasResult);
+  NS_ENSURE_TRUE(NS_SUCCEEDED(rv) && hasResult, NS_ERROR_FAILURE);
+
+  int32_t pageSize = 0;
+  rv = stmt->GetInt32(0, &pageSize);
+  NS_ENSURE_TRUE(NS_SUCCEEDED(rv) && pageSize > 0, NS_ERROR_UNEXPECTED);
+
+  // Set the threshold for auto-checkpointing the WAL.
+  // We don't want giant logs slowing down reads & shutdown.
+  int32_t thresholdInPages = static_cast<int32_t>(MAX_WAL_SIZE_BYTES / pageSize);
+  nsAutoCString thresholdPragma("PRAGMA wal_autocheckpoint = ");
+  thresholdPragma.AppendInt(thresholdInPages);
+  rv = mWorkerConnection->ExecuteSimpleSQL(thresholdPragma);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Set the maximum WAL log size to reduce footprint on mobile (large empty
+  // WAL files will be truncated)
+  nsAutoCString journalSizePragma("PRAGMA journal_size_limit = ");
+  // bug 600307: mak recommends setting this to 3 times the auto-checkpoint threshold
+  journalSizePragma.AppendInt(MAX_WAL_SIZE_BYTES * 3);
+  rv = mWorkerConnection->ExecuteSimpleSQL(journalSizePragma);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return NS_OK;
+}
+
+nsresult
+DOMStorageDBThread::ShutdownDatabase()
+{
+  // Has to be called on the worker thread.
+  MOZ_ASSERT(!NS_IsMainThread());
+
+  nsresult rv = mStatus;
+
+  mDBReady = false;
+
+  // Finalize the cached statements.
+  mReaderStatements.FinalizeStatements();
+  mWorkerStatements.FinalizeStatements();
+
+  if (mReaderConnection) {
+    // No need to sync access to mReaderConnection since the main thread
+    // is right now joining this thread, unable to execute any events.
+    mReaderConnection->Close();
+    mReaderConnection = nullptr;
+  }
+
+  if (mWorkerConnection) {
+    rv = mWorkerConnection->Close();
+    mWorkerConnection = nullptr;
+  }
+
+  return rv;
+}
+
+void
+DOMStorageDBThread::ScheduleFlush()
+{
+  if (mDirtyEpoch) {
+    return; // Already scheduled
+  }
+
+  mDirtyEpoch = PR_IntervalNow() | 1; // Must be non-zero to indicate we are scheduled
+
+  // Wake the monitor from indefinite sleep...
+  (mThreadObserver->GetMonitor()).Notify();
+}
+
+void
+DOMStorageDBThread::UnscheduleFlush()
+{
+  // We are just about to do the flush, drop flags
+  mFlushImmediately = false;
+  mDirtyEpoch = 0;
+}
+
+PRIntervalTime
+DOMStorageDBThread::TimeUntilFlush()
+{
+  if (mFlushImmediately) {
+    return 0; // Do it now regardless the timeout.
+  }
+
+  static_assert(PR_INTERVAL_NO_TIMEOUT != 0,
+      "PR_INTERVAL_NO_TIMEOUT must be non-zero");
+
+  if (!mDirtyEpoch) {
+    return PR_INTERVAL_NO_TIMEOUT; // No pending task...
+  }
+
+  static const PRIntervalTime kMaxAge = PR_MillisecondsToInterval(FLUSHING_INTERVAL_MS);
+
+  PRIntervalTime now = PR_IntervalNow() | 1;
+  PRIntervalTime age = now - mDirtyEpoch;
+  if (age > kMaxAge) {
+    return 0; // It is time.
+  }
+
+  return kMaxAge - age; // Time left, this is used to sleep the monitor
+}
+
+void
+DOMStorageDBThread::NotifyFlushCompletion()
+{
+#ifdef DOM_STORAGE_TESTS
+  if (!NS_IsMainThread()) {
+    RefPtr<nsRunnableMethod<DOMStorageDBThread, void, false> > event =
+      NewNonOwningRunnableMethod(this, &DOMStorageDBThread::NotifyFlushCompletion);
+    NS_DispatchToMainThread(event);
+    return;
+  }
+
+  nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
+  if (obs) {
+    obs->NotifyObservers(nullptr, "domstorage-test-flushed", nullptr);
+  }
+#endif
+}
+
+// Helper SQL function classes
+
+namespace {
+
+class OriginAttrsPatternMatchSQLFunction final : public mozIStorageFunction
+{
+  NS_DECL_ISUPPORTS
+  NS_DECL_MOZISTORAGEFUNCTION
+
+  explicit OriginAttrsPatternMatchSQLFunction(OriginAttributesPattern const& aPattern)
+    : mPattern(aPattern) {}
+
+private:
+  OriginAttrsPatternMatchSQLFunction() = delete;
+  ~OriginAttrsPatternMatchSQLFunction() {}
+
+  OriginAttributesPattern mPattern;
+};
+
+NS_IMPL_ISUPPORTS(OriginAttrsPatternMatchSQLFunction, mozIStorageFunction)
+
+NS_IMETHODIMP
+OriginAttrsPatternMatchSQLFunction::OnFunctionCall(
+    mozIStorageValueArray* aFunctionArguments, nsIVariant** aResult)
+{
+  nsresult rv;
+
+  nsAutoCString suffix;
+  rv = aFunctionArguments->GetUTF8String(0, suffix);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  PrincipalOriginAttributes oa;
+  bool success = oa.PopulateFromSuffix(suffix);
+  NS_ENSURE_TRUE(success, NS_ERROR_FAILURE);
+  bool result = mPattern.Matches(oa);
+
+  RefPtr<nsVariant> outVar(new nsVariant());
+  rv = outVar->SetAsBool(result);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  outVar.forget(aResult);
+  return NS_OK;
+}
+
+} // namespace
+
+// DOMStorageDBThread::DBOperation
+
+DOMStorageDBThread::DBOperation::DBOperation(const OperationType aType,
+                                             DOMStorageCacheBridge* aCache,
+                                             const nsAString& aKey,
+                                             const nsAString& aValue)
+: mType(aType)
+, mCache(aCache)
+, mKey(aKey)
+, mValue(aValue)
+{
+  MOZ_ASSERT(mType == opPreload ||
+             mType == opPreloadUrgent ||
+             mType == opAddItem ||
+             mType == opUpdateItem ||
+             mType == opRemoveItem ||
+             mType == opClear ||
+             mType == opClearAll);
+  MOZ_COUNT_CTOR(DOMStorageDBThread::DBOperation);
+}
+
+DOMStorageDBThread::DBOperation::DBOperation(const OperationType aType,
+                                             DOMStorageUsageBridge* aUsage)
+: mType(aType)
+, mUsage(aUsage)
+{
+  MOZ_ASSERT(mType == opGetUsage);
+  MOZ_COUNT_CTOR(DOMStorageDBThread::DBOperation);
+}
+
+DOMStorageDBThread::DBOperation::DBOperation(const OperationType aType,
+                                             const nsACString& aOriginNoSuffix)
+: mType(aType)
+, mCache(nullptr)
+, mOrigin(aOriginNoSuffix)
+{
+  MOZ_ASSERT(mType == opClearMatchingOrigin);
+  MOZ_COUNT_CTOR(DOMStorageDBThread::DBOperation);
+}
+
+DOMStorageDBThread::DBOperation::DBOperation(const OperationType aType,
+                                             const OriginAttributesPattern& aOriginNoSuffix)
+: mType(aType)
+, mCache(nullptr)
+, mOriginPattern(aOriginNoSuffix)
+{
+  MOZ_ASSERT(mType == opClearMatchingOriginAttributes);
+  MOZ_COUNT_CTOR(DOMStorageDBThread::DBOperation);
+}
+
+DOMStorageDBThread::DBOperation::~DBOperation()
+{
+  MOZ_COUNT_DTOR(DOMStorageDBThread::DBOperation);
+}
+
+const nsCString
+DOMStorageDBThread::DBOperation::OriginNoSuffix() const
+{
+  if (mCache) {
+    return mCache->OriginNoSuffix();
+  }
+
+  return EmptyCString();
+}
+
+const nsCString
+DOMStorageDBThread::DBOperation::OriginSuffix() const
+{
+  if (mCache) {
+    return mCache->OriginSuffix();
+  }
+
+  return EmptyCString();
+}
+
+const nsCString
+DOMStorageDBThread::DBOperation::Origin() const
+{
+  if (mCache) {
+    return mCache->Origin();
+  }
+
+  return mOrigin;
+}
+
+const nsCString
+DOMStorageDBThread::DBOperation::Target() const
+{
+  switch (mType) {
+    case opAddItem:
+    case opUpdateItem:
+    case opRemoveItem:
+      return Origin() + NS_LITERAL_CSTRING("|") + NS_ConvertUTF16toUTF8(mKey);
+
+    default:
+      return Origin();
+  }
+}
+
+void
+DOMStorageDBThread::DBOperation::PerformAndFinalize(DOMStorageDBThread* aThread)
+{
+  Finalize(Perform(aThread));
+}
+
+nsresult
+DOMStorageDBThread::DBOperation::Perform(DOMStorageDBThread* aThread)
+{
+  nsresult rv;
+
+  switch (mType) {
+  case opPreload:
+  case opPreloadUrgent:
+  {
+    // Already loaded?
+    if (mCache->Loaded()) {
+      break;
+    }
+
+    StatementCache* statements;
+    if (MOZ_UNLIKELY(NS_IsMainThread())) {
+      statements = &aThread->mReaderStatements;
+    } else {
+      statements = &aThread->mWorkerStatements;
+    }
+
+    // OFFSET is an optimization when we have to do a sync load
+    // and cache has already loaded some parts asynchronously.
+    // It skips keys we have already loaded.
+    nsCOMPtr<mozIStorageStatement> stmt = statements->GetCachedStatement(
+        "SELECT key, value FROM webappsstore2 "
+        "WHERE originAttributes = :originAttributes AND originKey = :originKey "
+        "ORDER BY key LIMIT -1 OFFSET :offset");
+    NS_ENSURE_STATE(stmt);
+    mozStorageStatementScoper scope(stmt);
+
+    rv = stmt->BindUTF8StringByName(NS_LITERAL_CSTRING("originAttributes"),
+                                    mCache->OriginSuffix());
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    rv = stmt->BindUTF8StringByName(NS_LITERAL_CSTRING("originKey"),
+                                    mCache->OriginNoSuffix());
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    rv = stmt->BindInt32ByName(NS_LITERAL_CSTRING("offset"),
+                               static_cast<int32_t>(mCache->LoadedCount()));
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    bool exists;
+    while (NS_SUCCEEDED(rv = stmt->ExecuteStep(&exists)) && exists) {
+      nsAutoString key;
+      rv = stmt->GetString(0, key);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      nsAutoString value;
+      rv = stmt->GetString(1, value);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      if (!mCache->LoadItem(key, value)) {
+        break;
+      }
+    }
+    // The loop condition's call to ExecuteStep() may have terminated because
+    // !NS_SUCCEEDED(), we need an early return to cover that case.  This also
+    // covers success cases as well, but that's inductively safe.
+    NS_ENSURE_SUCCESS(rv, rv);
+    break;
+  }
+
+  case opGetUsage:
+  {
+    nsCOMPtr<mozIStorageStatement> stmt = aThread->mWorkerStatements.GetCachedStatement(
+      "SELECT SUM(LENGTH(key) + LENGTH(value)) FROM webappsstore2 "
+      "WHERE (originAttributes || ':' || originKey) LIKE :usageOrigin"
+    );
+    NS_ENSURE_STATE(stmt);
+
+    mozStorageStatementScoper scope(stmt);
+
+    rv = stmt->BindUTF8StringByName(NS_LITERAL_CSTRING("usageOrigin"),
+                                    mUsage->OriginScope());
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    bool exists;
+    rv = stmt->ExecuteStep(&exists);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    int64_t usage = 0;
+    if (exists) {
+      rv = stmt->GetInt64(0, &usage);
+      NS_ENSURE_SUCCESS(rv, rv);
+    }
+
+    mUsage->LoadUsage(usage);
+    break;
+  }
+
+  case opAddItem:
+  case opUpdateItem:
+  {
+    MOZ_ASSERT(!NS_IsMainThread());
+
+    nsCOMPtr<mozIStorageStatement> stmt = aThread->mWorkerStatements.GetCachedStatement(
+      "INSERT OR REPLACE INTO webappsstore2 (originAttributes, originKey, scope, key, value) "
+      "VALUES (:originAttributes, :originKey, :scope, :key, :value) "
+    );
+    NS_ENSURE_STATE(stmt);
+
+    mozStorageStatementScoper scope(stmt);
+
+    rv = stmt->BindUTF8StringByName(NS_LITERAL_CSTRING("originAttributes"),
+                                    mCache->OriginSuffix());
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = stmt->BindUTF8StringByName(NS_LITERAL_CSTRING("originKey"),
+                                    mCache->OriginNoSuffix());
+    NS_ENSURE_SUCCESS(rv, rv);
+    // Filling the 'scope' column just for downgrade compatibility reasons
+    rv = stmt->BindUTF8StringByName(NS_LITERAL_CSTRING("scope"),
+                                    Scheme0Scope(mCache));
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = stmt->BindStringByName(NS_LITERAL_CSTRING("key"),
+                                mKey);
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = stmt->BindStringByName(NS_LITERAL_CSTRING("value"),
+                                mValue);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    rv = stmt->Execute();
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    MonitorAutoLock monitor(aThread->mThreadObserver->GetMonitor());
+    aThread->mOriginsHavingData.PutEntry(Origin());
+    break;
+  }
+
+  case opRemoveItem:
+  {
+    MOZ_ASSERT(!NS_IsMainThread());
+
+    nsCOMPtr<mozIStorageStatement> stmt = aThread->mWorkerStatements.GetCachedStatement(
+      "DELETE FROM webappsstore2 "
+      "WHERE originAttributes = :originAttributes AND originKey = :originKey "
+        "AND key = :key "
+    );
+    NS_ENSURE_STATE(stmt);
+    mozStorageStatementScoper scope(stmt);
+
+    rv = stmt->BindUTF8StringByName(NS_LITERAL_CSTRING("originAttributes"),
+                                    mCache->OriginSuffix());
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = stmt->BindUTF8StringByName(NS_LITERAL_CSTRING("originKey"),
+                                    mCache->OriginNoSuffix());
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = stmt->BindStringByName(NS_LITERAL_CSTRING("key"),
+                                mKey);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    rv = stmt->Execute();
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    break;
+  }
+
+  case opClear:
+  {
+    MOZ_ASSERT(!NS_IsMainThread());
+
+    nsCOMPtr<mozIStorageStatement> stmt = aThread->mWorkerStatements.GetCachedStatement(
+      "DELETE FROM webappsstore2 "
+      "WHERE originAttributes = :originAttributes AND originKey = :originKey"
+    );
+    NS_ENSURE_STATE(stmt);
+    mozStorageStatementScoper scope(stmt);
+
+    rv = stmt->BindUTF8StringByName(NS_LITERAL_CSTRING("originAttributes"),
+                                    mCache->OriginSuffix());
+    NS_ENSURE_SUCCESS(rv, rv);
+    rv = stmt->BindUTF8StringByName(NS_LITERAL_CSTRING("originKey"),
+                                    mCache->OriginNoSuffix());
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    rv = stmt->Execute();
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    MonitorAutoLock monitor(aThread->mThreadObserver->GetMonitor());
+    aThread->mOriginsHavingData.RemoveEntry(Origin());
+    break;
+  }
+
+  case opClearAll:
+  {
+    MOZ_ASSERT(!NS_IsMainThread());
+
+    nsCOMPtr<mozIStorageStatement> stmt = aThread->mWorkerStatements.GetCachedStatement(
+      "DELETE FROM webappsstore2"
+    );
+    NS_ENSURE_STATE(stmt);
+    mozStorageStatementScoper scope(stmt);
+
+    rv = stmt->Execute();
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    MonitorAutoLock monitor(aThread->mThreadObserver->GetMonitor());
+    aThread->mOriginsHavingData.Clear();
+    break;
+  }
+
+  case opClearMatchingOrigin:
+  {
+    MOZ_ASSERT(!NS_IsMainThread());
+
+    nsCOMPtr<mozIStorageStatement> stmt = aThread->mWorkerStatements.GetCachedStatement(
+      "DELETE FROM webappsstore2"
+      " WHERE originKey GLOB :scope"
+    );
+    NS_ENSURE_STATE(stmt);
+    mozStorageStatementScoper scope(stmt);
+
+    rv = stmt->BindUTF8StringByName(NS_LITERAL_CSTRING("scope"),
+                                    mOrigin + NS_LITERAL_CSTRING("*"));
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    rv = stmt->Execute();
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    // No need to selectively clear mOriginsHavingData here.  That hashtable only
+    // prevents preload for scopes with no data.  Leaving a false record in it has
+    // a negligible effect on performance.
+    break;
+  }
+
+  case opClearMatchingOriginAttributes:
+  {
+    MOZ_ASSERT(!NS_IsMainThread());
+
+    // Register the ORIGIN_ATTRS_PATTERN_MATCH function, initialized with the pattern
+    nsCOMPtr<mozIStorageFunction> patternMatchFunction(
+      new OriginAttrsPatternMatchSQLFunction(mOriginPattern));
+
+    rv = aThread->mWorkerConnection->CreateFunction(
+      NS_LITERAL_CSTRING("ORIGIN_ATTRS_PATTERN_MATCH"), 1, patternMatchFunction);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    nsCOMPtr<mozIStorageStatement> stmt = aThread->mWorkerStatements.GetCachedStatement(
+      "DELETE FROM webappsstore2"
+      " WHERE ORIGIN_ATTRS_PATTERN_MATCH(originAttributes)"
+    );
+
+    if (stmt) {
+      mozStorageStatementScoper scope(stmt);
+      rv = stmt->Execute();
+    } else {
+      rv = NS_ERROR_UNEXPECTED;
+    }
+
+    // Always remove the function
+    aThread->mWorkerConnection->RemoveFunction(
+      NS_LITERAL_CSTRING("ORIGIN_ATTRS_PATTERN_MATCH"));
+
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    // No need to selectively clear mOriginsHavingData here.  That hashtable only
+    // prevents preload for scopes with no data.  Leaving a false record in it has
+    // a negligible effect on performance.
+    break;
+  }
+
+  default:
+    NS_ERROR("Unknown task type");
+    break;
+  }
+
+  return NS_OK;
+}
+
+void
+DOMStorageDBThread::DBOperation::Finalize(nsresult aRv)
+{
+  switch (mType) {
+  case opPreloadUrgent:
+  case opPreload:
+    if (NS_FAILED(aRv)) {
+      // When we are here, something failed when loading from the database.
+      // Notify that the storage is loaded to prevent deadlock of the main thread,
+      // even though it is actually empty or incomplete.
+      NS_WARNING("Failed to preload localStorage");
+    }
+
+    mCache->LoadDone(aRv);
+    break;
+
+  case opGetUsage:
+    if (NS_FAILED(aRv)) {
+      mUsage->LoadUsage(0);
+    }
+
+    break;
+
+  default:
+    if (NS_FAILED(aRv)) {
+      NS_WARNING("localStorage update/clear operation failed,"
+                 " data may not persist or clean up");
+    }
+
+    break;
+  }
+}
+
+// DOMStorageDBThread::PendingOperations
+
+DOMStorageDBThread::PendingOperations::PendingOperations()
+: mFlushFailureCount(0)
+{
+}
+
+bool
+DOMStorageDBThread::PendingOperations::HasTasks() const
+{
+  return !!mUpdates.Count() || !!mClears.Count();
+}
+
+namespace {
+
+bool OriginPatternMatches(const nsACString& aOriginSuffix, const OriginAttributesPattern& aPattern)
+{
+  PrincipalOriginAttributes oa;
+  DebugOnly<bool> rv = oa.PopulateFromSuffix(aOriginSuffix);
+  MOZ_ASSERT(rv);
+  return aPattern.Matches(oa);
+}
+
+} // namespace
+
+bool
+DOMStorageDBThread::PendingOperations::CheckForCoalesceOpportunity(DBOperation* aNewOp,
+                                                                   DBOperation::OperationType aPendingType,
+                                                                   DBOperation::OperationType aNewType)
+{
+  if (aNewOp->Type() != aNewType) {
+    return false;
+  }
+
+  DOMStorageDBThread::DBOperation* pendingTask;
+  if (!mUpdates.Get(aNewOp->Target(), &pendingTask)) {
+    return false;
+  }
+
+  if (pendingTask->Type() != aPendingType) {
+    return false;
+  }
+
+  return true;
+}
+
+void
+DOMStorageDBThread::PendingOperations::Add(DOMStorageDBThread::DBOperation* aOperation)
+{
+  // Optimize: when a key to remove has never been written to disk
+  // just bypass this operation.  A key is new when an operation scheduled
+  // to write it to the database is of type opAddItem.
+  if (CheckForCoalesceOpportunity(aOperation, DBOperation::opAddItem, DBOperation::opRemoveItem)) {
+    mUpdates.Remove(aOperation->Target());
+    delete aOperation;
+    return;
+  }
+
+  // Optimize: when changing a key that is new and has never been
+  // written to disk, keep type of the operation to store it at opAddItem.
+  // This allows optimization to just forget adding a new key when
+  // it is removed from the storage before flush.
+  if (CheckForCoalesceOpportunity(aOperation, DBOperation::opAddItem, DBOperation::opUpdateItem)) {
+    aOperation->mType = DBOperation::opAddItem;
+  }
+
+  // Optimize: to prevent lose of remove operation on a key when doing
+  // remove/set/remove on a previously existing key we have to change
+  // opAddItem to opUpdateItem on the new operation when there is opRemoveItem
+  // pending for the key.
+  if (CheckForCoalesceOpportunity(aOperation, DBOperation::opRemoveItem, DBOperation::opAddItem)) {
+    aOperation->mType = DBOperation::opUpdateItem;
+  }
+
+  switch (aOperation->Type())
+  {
+  // Operations on single keys
+
+  case DBOperation::opAddItem:
+  case DBOperation::opUpdateItem:
+  case DBOperation::opRemoveItem:
+    // Override any existing operation for the target (=scope+key).
+    mUpdates.Put(aOperation->Target(), aOperation);
+    break;
+
+  // Clear operations
+
+  case DBOperation::opClear:
+  case DBOperation::opClearMatchingOrigin:
+  case DBOperation::opClearMatchingOriginAttributes:
+    // Drop all update (insert/remove) operations for equivavelent or matching scope.
+    // We do this as an optimization as well as a must based on the logic,
+    // if we would not delete the update tasks, changes would have been stored
+    // to the database after clear operations have been executed.
+    for (auto iter = mUpdates.Iter(); !iter.Done(); iter.Next()) {
+      nsAutoPtr<DBOperation>& pendingTask = iter.Data();
+
+      if (aOperation->Type() == DBOperation::opClear &&
+          (pendingTask->OriginNoSuffix() != aOperation->OriginNoSuffix() ||
+           pendingTask->OriginSuffix() != aOperation->OriginSuffix())) {
+        continue;
+      }
+
+      if (aOperation->Type() == DBOperation::opClearMatchingOrigin &&
+          !StringBeginsWith(pendingTask->OriginNoSuffix(), aOperation->Origin())) {
+        continue;
+      }
+
+      if (aOperation->Type() == DBOperation::opClearMatchingOriginAttributes &&
+          !OriginPatternMatches(pendingTask->OriginSuffix(), aOperation->OriginPattern())) {
+        continue;
+      }
+
+      iter.Remove();
+    }
+
+    mClears.Put(aOperation->Target(), aOperation);
+    break;
+
+  case DBOperation::opClearAll:
+    // Drop simply everything, this is a super-operation.
+    mUpdates.Clear();
+    mClears.Clear();
+    mClears.Put(aOperation->Target(), aOperation);
+    break;
+
+  default:
+    MOZ_ASSERT(false);
+    break;
+  }
+}
+
+bool
+DOMStorageDBThread::PendingOperations::Prepare()
+{
+  // Called under the lock
+
+  // First collect clear operations and then updates, we can
+  // do this since whenever a clear operation for a scope is
+  // scheduled, we drop all updates matching that scope. So,
+  // all scope-related update operations we have here now were
+  // scheduled after the clear operations.
+  for (auto iter = mClears.Iter(); !iter.Done(); iter.Next()) {
+    mExecList.AppendElement(iter.Data().forget());
+  }
+  mClears.Clear();
+
+  for (auto iter = mUpdates.Iter(); !iter.Done(); iter.Next()) {
+    mExecList.AppendElement(iter.Data().forget());
+  }
+  mUpdates.Clear();
+
+  return !!mExecList.Length();
+}
+
+nsresult
+DOMStorageDBThread::PendingOperations::Execute(DOMStorageDBThread* aThread)
+{
+  // Called outside the lock
+
+  mozStorageTransaction transaction(aThread->mWorkerConnection, false);
+
+  nsresult rv;
+
+  for (uint32_t i = 0; i < mExecList.Length(); ++i) {
+    DOMStorageDBThread::DBOperation* task = mExecList[i];
+    rv = task->Perform(aThread);
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+  }
+
+  rv = transaction.Commit();
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  return NS_OK;
+}
+
+bool
+DOMStorageDBThread::PendingOperations::Finalize(nsresult aRv)
+{
+  // Called under the lock
+
+  // The list is kept on a failure to retry it
+  if (NS_FAILED(aRv)) {
+    // XXX Followup: we may try to reopen the database and flush these
+    // pending tasks, however testing showed that even though I/O is actually
+    // broken some amount of operations is left in sqlite+system buffers and
+    // seems like successfully flushed to disk.
+    // Tested by removing a flash card and disconnecting from network while
+    // using a network drive on Windows system.
+    NS_WARNING("Flush operation on localStorage database failed");
+
+    ++mFlushFailureCount;
+
+    return mFlushFailureCount >= 5;
+  }
+
+  mFlushFailureCount = 0;
+  mExecList.Clear();
+  return true;
+}
+
+namespace {
+
+bool
+FindPendingClearForOrigin(const nsACString& aOriginSuffix, const nsACString& aOriginNoSuffix,
+                         DOMStorageDBThread::DBOperation* aPendingOperation)
+{
+  if (aPendingOperation->Type() == DOMStorageDBThread::DBOperation::opClearAll) {
+    return true;
+  }
+
+  if (aPendingOperation->Type() == DOMStorageDBThread::DBOperation::opClear &&
+      aOriginNoSuffix == aPendingOperation->OriginNoSuffix() &&
+      aOriginSuffix == aPendingOperation->OriginSuffix()) {
+    return true;
+  }
+
+  if (aPendingOperation->Type() == DOMStorageDBThread::DBOperation::opClearMatchingOrigin &&
+      StringBeginsWith(aOriginNoSuffix, aPendingOperation->Origin())) {
+    return true;
+  }
+
+  if (aPendingOperation->Type() == DOMStorageDBThread::DBOperation::opClearMatchingOriginAttributes &&
+      OriginPatternMatches(aOriginSuffix, aPendingOperation->OriginPattern())) {
+    return true;
+  }
+
+  return false;
+}
+
+} // namespace
+
+bool
+DOMStorageDBThread::PendingOperations::IsOriginClearPending(const nsACString& aOriginSuffix,
+                                                            const nsACString& aOriginNoSuffix) const
+{
+  // Called under the lock
+
+  for (auto iter = mClears.ConstIter(); !iter.Done(); iter.Next()) {
+    if (FindPendingClearForOrigin(aOriginSuffix, aOriginNoSuffix, iter.UserData())) {
+      return true;
+    }
+  }
+
+  for (uint32_t i = 0; i < mExecList.Length(); ++i) {
+    if (FindPendingClearForOrigin(aOriginSuffix, aOriginNoSuffix, mExecList[i])) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+namespace {
+
+bool
+FindPendingUpdateForOrigin(const nsACString& aOriginSuffix, const nsACString& aOriginNoSuffix,
+                           DOMStorageDBThread::DBOperation* aPendingOperation)
+{
+  if ((aPendingOperation->Type() == DOMStorageDBThread::DBOperation::opAddItem ||
+       aPendingOperation->Type() == DOMStorageDBThread::DBOperation::opUpdateItem ||
+       aPendingOperation->Type() == DOMStorageDBThread::DBOperation::opRemoveItem) &&
+       aOriginNoSuffix == aPendingOperation->OriginNoSuffix() &&
+       aOriginSuffix == aPendingOperation->OriginSuffix()) {
+    return true;
+  }
+
+  return false;
+}
+
+} // namespace
+
+bool
+DOMStorageDBThread::PendingOperations::IsOriginUpdatePending(const nsACString& aOriginSuffix,
+                                                             const nsACString& aOriginNoSuffix) const
+{
+  // Called under the lock
+
+  for (auto iter = mUpdates.ConstIter(); !iter.Done(); iter.Next()) {
+    if (FindPendingUpdateForOrigin(aOriginSuffix, aOriginNoSuffix, iter.UserData())) {
+      return true;
+    }
+  }
+
+  for (uint32_t i = 0; i < mExecList.Length(); ++i) {
+    if (FindPendingUpdateForOrigin(aOriginSuffix, aOriginNoSuffix, mExecList[i])) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+} // namespace dom
+} // namespace mozilla