Allows turning on checked mode on a per-isolate basis

runtime/vm/intrinsifier_ia32.cc

Index: runtime/vm/intrinsifier_ia32.cc
===================================================================
--- runtime/vm/intrinsifier_ia32.cc	(revision 43426)
+++ runtime/vm/intrinsifier_ia32.cc	(working copy)
@@ -33,6 +33,11 @@
 intptr_t Intrinsifier::ParameterSlotFromSp() { return 0; }
 
 
+static bool TypeChecksEnabled() {
+  return FLAG_enable_type_checks || Isolate::Current()->checked_mode();
+}
+
+
 static intptr_t ComputeObjectArrayTypeArgumentsOffset() {
   const Library& core_lib = Library::Handle(Library::CoreLibrary());
   const Class& cls = Class::Handle(
@@ -49,7 +54,7 @@
 // update. Array length is always a Smi.
 void Intrinsifier::ObjectArraySetIndexed(Assembler* assembler) {
   Label fall_through;
-  if (FLAG_enable_type_checks) {
+  if (TypeChecksEnabled()) {
     const intptr_t type_args_field_offset =
         ComputeObjectArrayTypeArgumentsOffset();
     // Inline simple tests (Smi, null), fallthrough if not positive.
@@ -150,7 +155,7 @@
 // On stack: growable array (+2), value (+1), return-address (+0).
 void Intrinsifier::GrowableArray_add(Assembler* assembler) {
   // In checked mode we need to type-check the incoming argument.
-  if (FLAG_enable_type_checks) return;
+  if (TypeChecksEnabled()) return;
 
   Label fall_through;
   __ movl(EAX, Address(ESP, + 2 * kWordSize));  // Array.