Fix SQLStatementBackend::m_resultSet to use CrossThreadPersistent

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

Index: third_party/WebKit/Source/modules/webdatabase/SQLStatementBackend.cpp
diff --git a/third_party/WebKit/Source/modules/webdatabase/SQLStatementBackend.cpp b/third_party/WebKit/Source/modules/webdatabase/SQLStatementBackend.cpp
index d67754efb88ab67cf03fc758c4441f94e0917765..cdba5c33a976eff3225e3cabf7692f5390ede58f 100644
--- a/third_party/WebKit/Source/modules/webdatabase/SQLStatementBackend.cpp
+++ b/third_party/WebKit/Source/modules/webdatabase/SQLStatementBackend.cpp
@@ -108,7 +108,6 @@ SQLStatementBackend::SQLStatementBackend(SQLStatement* frontend,
 
 DEFINE_TRACE(SQLStatementBackend) {
   visitor->trace(m_frontend);
-  visitor->trace(m_resultSet);
 }
 
 SQLStatement* SQLStatementBackend::frontend() {
@@ -193,7 +192,7 @@ bool SQLStatementBackend::execute(Database* db) {
   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));