Check that Dart_CreateIsolate is given a correct kind of snapshot.

runtime/vm/dart.cc

Index: runtime/vm/dart.cc
diff --git a/runtime/vm/dart.cc b/runtime/vm/dart.cc
index 579691ec6714e39e4bd61ad73e82ef08cacc7460..43aebebeb33fe50c242baf2fe59559151ee9544e 100644
--- a/runtime/vm/dart.cc
+++ b/runtime/vm/dart.cc
@@ -530,8 +530,14 @@ RawError* Dart::InitializeIsolate(const uint8_t* snapshot_buffer, void* data) {
           String::New("Invalid snapshot"));
       return ApiError::New(message);
     }
+    if (snapshot->kind() != snapshot_kind_) {
+      const String& message = String::Handle(
+          String::NewFormatted("Invalid snapshot kind: got '%s', expected '%s'",
+                               Snapshot::KindToCString(snapshot->kind()),
+                               Snapshot::KindToCString(snapshot_kind_)));
+      return ApiError::New(message);
+    }
     ASSERT(Snapshot::IsFull(snapshot->kind()));
-    ASSERT(snapshot->kind() == snapshot_kind_);
     if (FLAG_trace_isolates) {
       OS::Print("Size of isolate snapshot = %" Pd "\n", snapshot->length());
     }