Precompilation:

runtime/vm/dart.cc

Index: runtime/vm/dart.cc
diff --git a/runtime/vm/dart.cc b/runtime/vm/dart.cc
index 340dfd57c930d95b9275048650a5cd4dec2a3fcb..d8367fe08b60df471165372de3d5484b4ad099d2 100644
--- a/runtime/vm/dart.cc
+++ b/runtime/vm/dart.cc
@@ -161,6 +161,8 @@ const char* Dart::InitOnce(const uint8_t* vm_isolate_snapshot,
       StubCode::InitOnce();
     }
     if (vm_isolate_snapshot != NULL) {
+      NOT_IN_PRODUCT(TimelineDurationScope tds(Timeline::GetVMStream(),
+                                               "VMIsolateSnapshot"));
       if (data_snapshot != NULL) {
         vm_isolate_->SetupDataSnapshotPage(data_snapshot);
       }
@@ -202,7 +204,11 @@ const char* Dart::InitOnce(const uint8_t* vm_isolate_snapshot,
       return "SSE2 is required.";
     }
 #endif
-    Object::FinalizeVMIsolate(vm_isolate_);
+    {
+      NOT_IN_PRODUCT(TimelineDurationScope tds(Timeline::GetVMStream(),
+                                               "FinalizeVMIsolate"));
+      Object::FinalizeVMIsolate(vm_isolate_);
+    }
 #if defined(DEBUG)
     vm_isolate_->heap()->Verify(kRequireMarked);
 #endif