Make the VM resilient to a confusion between a NULL instructions snapshot and instructions snapshot…

runtime/vm/clustered_snapshot.cc

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/clustered_snapshot.h"
 
 #include "platform/assert.h"
 #include "vm/bootstrap.h"
 #include "vm/class_finalizer.h"
 #include "vm/dart.h"
@@ skipping 5461 matching lines @@
 
 RawApiError* FullSnapshotReader::ReadVMSnapshot() {
   Deserializer deserializer(thread_, kind_, buffer_, size_,
                             instructions_buffer_, data_buffer_);
 
   RawApiError* error = deserializer.VerifyVersionAndFeatures();
   if (error != ApiError::null()) {
     return error;
   }
 
-  if (instructions_buffer_ != NULL) {
+  if (Snapshot::IncludesCode(kind_)) {
+    ASSERT(instructions_buffer_ != NULL);
     thread_->isolate()->SetupInstructionsSnapshotPage(instructions_buffer_);
-  }
-  if (data_buffer_ != NULL) {
+    ASSERT(data_buffer_ != NULL);
     thread_->isolate()->SetupDataSnapshotPage(data_buffer_);
   }
 
   deserializer.ReadVMSnapshot();
 
   return ApiError::null();
 }
 
 
 RawApiError* FullSnapshotReader::ReadIsolateSnapshot() {
   Deserializer deserializer(thread_, kind_, buffer_, size_,
                             instructions_buffer_, data_buffer_);
 
   RawApiError* error = deserializer.VerifyVersionAndFeatures();
   if (error != ApiError::null()) {
     return error;
   }
 
-  if (instructions_buffer_ != NULL) {
+  if (Snapshot::IncludesCode(kind_)) {
+    ASSERT(instructions_buffer_ != NULL);
     thread_->isolate()->SetupInstructionsSnapshotPage(instructions_buffer_);
-  }
-  if (data_buffer_ != NULL) {
+    ASSERT(data_buffer_ != NULL);
     thread_->isolate()->SetupDataSnapshotPage(data_buffer_);
   }
 
   deserializer.ReadIsolateSnapshot(thread_->isolate()->object_store());
 
   return ApiError::null();
 }
 
 }  // namespace dart