Protecting against other possible uses of invalid V8 execution context.

Speculative fix for a user reported crash when a worker with an active IndexedDB
transaction was terminated. This stack is very similar to the one for 345354. I
do not have a reproduction for this bug was unable to verify that it fixes the
problem, but checking for a stopped context is still a good idea.

BUG=356146, 356171

Review URL: https://codereview.chromium.org/213073004

git-svn-id: svn://svn.chromium.org/blink/trunk@170107 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/modules/indexeddb/IDBDatabase.cpp

@@ -379,6 +379,8 @@ void IDBDatabase::enqueueEvent(PassRefPtr<Event> event)
 bool IDBDatabase::dispatchEvent(PassRefPtr<Event> event)
 {
     IDB_TRACE("IDBDatabase::dispatchEvent");
+    if (m_contextStopped || !executionContext())
+        return false;
     ASSERT(event->type() == EventTypeNames::versionchange || event->type() == EventTypeNames::close);
     for (size_t i = 0; i < m_enqueuedEvents.size(); ++i) {
         if (m_enqueuedEvents[i].get() == event.get())

third_party/WebKit/Source/modules/indexeddb/IDBTransaction.cpp

@@ -341,6 +341,10 @@ ExecutionContext* IDBTransaction::executionContext() const
 bool IDBTransaction::dispatchEvent(PassRefPtr<Event> event)
 {
     IDB_TRACE("IDBTransaction::dispatchEvent");
+    if (m_contextStopped || !executionContext()) {
+        m_state = Finished;
+        return false;
+    }
     ASSERT(m_state != Finished);
     ASSERT(m_hasPendingActivity);
     ASSERT(executionContext());