Use zone when allocating handles in FlowGraphCompiler assembling operations. Add profiling VM tags…

runtime/vm/tags.cc

Index: runtime/vm/tags.cc
diff --git a/runtime/vm/tags.cc b/runtime/vm/tags.cc
index 50e5e237d34a6e2ed5f404aae65ef71e24f6b72b..ffd224f7aa45ab7b1b9fdb70ab3a76bb44b958eb 100644
--- a/runtime/vm/tags.cc
+++ b/runtime/vm/tags.cc
@@ -81,11 +81,13 @@ VMTag::TagEntry VMTag::entries_[] = {
 };
 
 
-VMTagScope::VMTagScope(Isolate* base_isolate, uword tag)
+VMTagScope::VMTagScope(Isolate* base_isolate, uword tag, bool conditional_set)
     : StackResource(base_isolate) {
   ASSERT(isolate() != NULL);
   previous_tag_ = isolate()->vm_tag();
-  isolate()->set_vm_tag(tag);
+  if (conditional_set) {
+    isolate()->set_vm_tag(tag);
+  }
 }