Improve internal compiler API so that OSR code is never installed on function.

runtime/vm/dart_entry.cc

Index: runtime/vm/dart_entry.cc
diff --git a/runtime/vm/dart_entry.cc b/runtime/vm/dart_entry.cc
index 195781cd5044c03bf337b3f468268c5791419107..a333fde4e78f7c17af961bf768ddf8be30effc64 100644
--- a/runtime/vm/dart_entry.cc
+++ b/runtime/vm/dart_entry.cc
@@ -96,10 +96,10 @@ RawObject* DartEntry::InvokeFunction(const Function& function,
   ASSERT(thread->IsMutatorThread());
   ScopedIsolateStackLimits stack_limit(thread, current_sp);
   if (!function.HasCode()) {
-    const Error& error =
-        Error::Handle(zone, Compiler::CompileFunction(thread, function));
-    if (!error.IsNull()) {
-      return error.raw();
+    const Object& result =
+        Object::Handle(zone, Compiler::CompileFunction(thread, function));
+    if (result.IsError()) {
+      return Error::Cast(result).raw();
     }
   }
 // Now Call the invoke stub which will invoke the dart function.