Refactor the Heap into ThreadHeap to prepare for per thread heaps

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

Index: third_party/WebKit/Source/modules/webdatabase/SQLTransactionCoordinator.cpp
diff --git a/third_party/WebKit/Source/modules/webdatabase/SQLTransactionCoordinator.cpp b/third_party/WebKit/Source/modules/webdatabase/SQLTransactionCoordinator.cpp
index 16b1356c323c272f2de2655d6122d473bcbf85e9..008651bb4295e9f11759e690bc03852cf986e01f 100644
--- a/third_party/WebKit/Source/modules/webdatabase/SQLTransactionCoordinator.cpp
+++ b/third_party/WebKit/Source/modules/webdatabase/SQLTransactionCoordinator.cpp
@@ -46,11 +46,11 @@ static String getDatabaseIdentifier(SQLTransactionBackend* transaction)
 SQLTransactionCoordinator::SQLTransactionCoordinator()
     : m_isShuttingDown(false)
 {
+    ASSERT(isMainThread());
 }
 
 DEFINE_TRACE(SQLTransactionCoordinator)
 {
-    visitor->trace(m_coordinationInfoMap);
 }
 
 void SQLTransactionCoordinator::processPendingTransactions(CoordinationInfo& info)
@@ -130,11 +130,8 @@ void SQLTransactionCoordinator::shutdown()
         // transaction is interrupted?" at the top of SQLTransactionBackend.cpp.
         if (info.activeWriteTransaction)
             info.activeWriteTransaction->notifyDatabaseThreadIsShuttingDown();
-        for (HeapHashSet<Member<SQLTransactionBackend>>::iterator activeReadTransactionsIterator =
-                     info.activeReadTransactions.begin();
-             activeReadTransactionsIterator != info.activeReadTransactions.end();
-             ++activeReadTransactionsIterator) {
-            (*activeReadTransactionsIterator)->notifyDatabaseThreadIsShuttingDown();
+        for (auto& it : info.activeReadTransactions) {
+            it->notifyDatabaseThreadIsShuttingDown();
         }
 
         // Clean up transactions that have NOT reached "lockAcquired":