Allows turning on checked mode on a per-isolate basis

runtime/vm/flow_graph_type_propagator.cc

Index: runtime/vm/flow_graph_type_propagator.cc
===================================================================
--- runtime/vm/flow_graph_type_propagator.cc	(revision 43426)
+++ runtime/vm/flow_graph_type_propagator.cc	(working copy)
@@ -19,6 +19,11 @@
 DECLARE_FLAG(bool, use_cha);
 
 
+static bool TypeChecksEnabled() {
+  return FLAG_enable_type_checks || Isolate::Current()->checked_mode();
+}
+
+
 void FlowGraphTypePropagator::Propagate(FlowGraph* flow_graph) {
   FlowGraphTypePropagator propagator(flow_graph);
   propagator.Propagate();
@@ -39,7 +44,7 @@
     types_.Add(NULL);
   }
 
-  if (FLAG_enable_type_checks) {
+  if (TypeChecksEnabled()) {
     asserts_ = new ZoneGrowableArray<AssertAssignableInstr*>(
         flow_graph->current_ssa_temp_index());
     for (intptr_t i = 0; i < flow_graph->current_ssa_temp_index(); i++) {
@@ -121,7 +126,7 @@
 
   const intptr_t rollback_point = rollback_.length();
 
-  if (FLAG_enable_type_checks) {
+  if (TypeChecksEnabled()) {
     StrengthenAsserts(block);
   }
 
@@ -895,7 +900,7 @@
     return CompileType::FromCid(result_cid_);
   }
 
-  if (FLAG_enable_type_checks) {
+  if (TypeChecksEnabled()) {
     // Void functions are known to return null, which is checked at the return
     // from the function.
     const AbstractType& result_type =
@@ -910,7 +915,7 @@
 
 
 CompileType LoadLocalInstr::ComputeType() const {
-  if (FLAG_enable_type_checks) {
+  if (TypeChecksEnabled()) {
     return CompileType::FromAbstractType(local().type());
   }
   return CompileType::Dynamic();
@@ -954,7 +959,7 @@
   intptr_t cid = kDynamicCid;
   AbstractType* abstract_type = NULL;
   const Field& field = this->StaticField();
-  if (FLAG_enable_type_checks) {
+  if (TypeChecksEnabled()) {
     cid = kIllegalCid;
     abstract_type = &AbstractType::ZoneHandle(field.type());
   }
@@ -1009,7 +1014,7 @@
   }
 
   const AbstractType* abstract_type = NULL;
-  if (FLAG_enable_type_checks) {
+  if (TypeChecksEnabled()) {
     ASSERT(!type().HasResolvedTypeClass() ||
            !Field::IsExternalizableCid(Class::Handle(
                 type().type_class()).id()));