Refactor the Heap into ThreadHeap to prepare for per thread heaps

third_party/WebKit/Source/modules/webdatabase/Database.cpp

Index: third_party/WebKit/Source/modules/webdatabase/Database.cpp
diff --git a/third_party/WebKit/Source/modules/webdatabase/Database.cpp b/third_party/WebKit/Source/modules/webdatabase/Database.cpp
index 49172e398407040128481fd2e1554d7e8fd9f28a..1b7eaab5762526bbe7066ededbfe29558b9e667d 100644
--- a/third_party/WebKit/Source/modules/webdatabase/Database.cpp
+++ b/third_party/WebKit/Source/modules/webdatabase/Database.cpp
@@ -213,6 +213,7 @@ Database::Database(DatabaseContext* databaseContext, const String& name, const S
     , m_transactionInProgress(false)
     , m_isTransactionQueueEnabled(true)
 {
+    ASSERT(isMainThread());
     m_contextThreadSecurityOrigin = m_databaseContext->securityOrigin()->isolatedCopy();
 
     m_databaseAuthorizer = DatabaseAuthorizer::create(infoTableName);
@@ -282,8 +283,8 @@ void Database::close()
         // Transaction phase 1 cleanup. See comment on "What happens if a
         // transaction is interrupted?" at the top of SQLTransactionBackend.cpp.
         SQLTransactionBackend* transaction = nullptr;
-        while (!m_transactionQueue.isEmpty()) {
-            transaction = m_transactionQueue.takeFirst();
+        while (m_transactionQueue && !m_transactionQueue->isEmpty()) {
+            transaction = m_transactionQueue->takeFirst();
             transaction->notifyDatabaseThreadIsShuttingDown();
         }
 
@@ -306,7 +307,9 @@ SQLTransactionBackend* Database::runTransaction(SQLTransaction* transaction, boo
         wrapper = ChangeVersionWrapper::create(data->oldVersion(), data->newVersion());
 
     SQLTransactionBackend* transactionBackend = SQLTransactionBackend::create(this, transaction, wrapper, readOnly);
-    m_transactionQueue.append(transactionBackend);
+    if (!m_transactionQueue)
+        m_transactionQueue = new HeapDeque<Member<SQLTransactionBackend>>();
+    m_transactionQueue->append(transactionBackend);
     if (!m_transactionInProgress)
         scheduleTransaction();
 
@@ -325,8 +328,8 @@ void Database::scheduleTransaction()
     ASSERT(!m_transactionInProgressMutex.tryLock()); // Locked by caller.
     SQLTransactionBackend* transaction = nullptr;
 
-    if (m_isTransactionQueueEnabled && !m_transactionQueue.isEmpty())
-        transaction = m_transactionQueue.takeFirst();
+    if (m_isTransactionQueueEnabled && m_transactionQueue && !m_transactionQueue->isEmpty())
+        transaction = m_transactionQueue->takeFirst();
 
     if (transaction && databaseContext()->databaseThreadAvailable()) {
         OwnPtr<DatabaseTransactionTask> task = DatabaseTransactionTask::create(transaction);