Add simple VM test for precompiled code.

runtime/vm/isolate.cc

Index: runtime/vm/isolate.cc
diff --git a/runtime/vm/isolate.cc b/runtime/vm/isolate.cc
index 685e457309e103c72e593b692c8b3003ee86495b..2d0e7cf56ee2b328a14f81abc94b4635ea3daf0f 100644
--- a/runtime/vm/isolate.cc
+++ b/runtime/vm/isolate.cc
@@ -897,10 +897,12 @@ void Isolate::SetupInstructionsSnapshotPage(
     const uint8_t* instructions_snapshot_buffer) {
   InstructionsSnapshot snapshot(instructions_snapshot_buffer);
 #if defined(DEBUG)
-  OS::Print("Precompiled instructions are at [0x%" Px ", 0x%" Px ")\n",
-            reinterpret_cast<uword>(snapshot.instructions_start()),
-            reinterpret_cast<uword>(snapshot.instructions_start()) +
-            snapshot.instructions_size());
+  if (FLAG_trace_isolates) {
+    OS::Print("Precompiled instructions are at [0x%" Px ", 0x%" Px ")\n",
+              reinterpret_cast<uword>(snapshot.instructions_start()),
+              reinterpret_cast<uword>(snapshot.instructions_start()) +
+              snapshot.instructions_size());
+  }
 #endif
   heap_->SetupInstructionsSnapshotPage(snapshot.instructions_start(),
                                        snapshot.instructions_size());