Add more timing information in the VM to track time spent is dart code Vs native code.

runtime/vm/dart_entry.cc

Index: runtime/vm/dart_entry.cc
===================================================================
--- runtime/vm/dart_entry.cc	(revision 32362)
+++ runtime/vm/dart_entry.cc	(working copy)
@@ -52,23 +52,25 @@
     }
   }
   // Now Call the invoke stub which will invoke the dart function.
+  Isolate* isolate = Isolate::Current();
+  TIMERSCOPE(isolate, time_dart_execution);
   invokestub entrypoint = reinterpret_cast<invokestub>(
       StubCode::InvokeDartCodeEntryPoint());
-  const Code& code = Code::Handle(function.CurrentCode());
+  const Code& code = Code::Handle(isolate, function.CurrentCode());
   ASSERT(!code.IsNull());
-  ASSERT(Isolate::Current()->no_callback_scope_depth() == 0);
+  ASSERT(isolate->no_callback_scope_depth() == 0);
 #if defined(USING_SIMULATOR)
-    return bit_copy<RawObject*, int64_t>(Simulator::Current()->Call(
-        reinterpret_cast<int32_t>(entrypoint),
-        static_cast<int32_t>(code.EntryPoint()),
-        reinterpret_cast<int32_t>(&arguments_descriptor),
-        reinterpret_cast<int32_t>(&arguments),
-        reinterpret_cast<int32_t>(&context)));
+  return bit_copy<RawObject*, int64_t>(Simulator::Current()->Call(
+      reinterpret_cast<int32_t>(entrypoint),
+      static_cast<int32_t>(code.EntryPoint()),
+      reinterpret_cast<int32_t>(&arguments_descriptor),
+      reinterpret_cast<int32_t>(&arguments),
+      reinterpret_cast<int32_t>(&context)));
 #else
-    return entrypoint(code.EntryPoint(),
-                      arguments_descriptor,
-                      arguments,
-                      context);
+  return entrypoint(code.EntryPoint(),
+                    arguments_descriptor,
+                    arguments,
+                    context);
 #endif
 }