Fix SQLStatementBackend::m_resultSet to use CrossThreadPersistent

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

 /*
  * Copyright (C) 2007, 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 90 matching lines @@
       m_hasErrorCallback(m_frontend->hasErrorCallback()),
       m_resultSet(SQLResultSet::create()),
       m_permissions(permissions) {
   DCHECK(isMainThread());
 
   m_frontend->setBackend(this);
 }
 
 DEFINE_TRACE(SQLStatementBackend) {
   visitor->trace(m_frontend);
-  visitor->trace(m_resultSet);
 }
 
 SQLStatement* SQLStatementBackend::frontend() {
   return m_frontend.get();
 }
 
 SQLErrorData* SQLStatementBackend::sqlError() const {
   return m_error.get();
 }
 
@@ skipping 64 matching lines @@
           SQLErrorData::create(SQLError::kDatabaseErr, "could not bind value",
                                result, database->lastErrorMsg());
       return false;
     }
   }
 
   // Step so we can fetch the column names.
   result = statement.step();
   if (result == SQLResultRow) {
     int columnCount = statement.columnCount();
-    SQLResultSetRowList* rows = m_resultSet->rows();
+    CrossThreadPersistent<SQLResultSetRowList> rows = m_resultSet->rows();

[sof, 2017/01/17 14:13:03]

This too I'm also not understanding -- if a thread is working over an object O
from another heap, then keeping O alive with a CTP while the thread uses it
should be sufficient to keep everything it refers to alive.

Having to create CTPs like this for stack references, shouldn't be needed.. and
looks tricky to maintain correctness for.

 
     for (int i = 0; i < columnCount; i++)
       rows->addColumn(statement.getColumnName(i));
 
     do {
       for (int i = 0; i < columnCount; i++)
         rows->addResult(statement.getColumnValue(i));
 
       result = statement.step();
     } while (result == SQLResultRow);
@@ skipping 59 matching lines @@
 void SQLStatementBackend::clearFailureDueToQuota() {
   if (lastExecutionFailedDueToQuota())
     m_error = nullptr;
 }
 
 bool SQLStatementBackend::lastExecutionFailedDueToQuota() const {
   return m_error && m_error->code() == SQLError::kQuotaErr;
 }
 
 }  // namespace blink