When creating a JIT app snapshot, don't recreate the VM isolate snapshot.

runtime/vm/pages.cc

 // Copyright (c) 2012, 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/pages.h"
 
 #include "platform/assert.h"
 #include "vm/compiler_stats.h"
 #include "vm/gc_marker.h"
 #include "vm/gc_sweeper.h"
@@ skipping 121 matching lines @@
       }
       obj_addr = next_obj_addr;
     }
     ASSERT(obj_addr == end_addr);
   }
   return Object::null();
 }
 
 
 void HeapPage::WriteProtect(bool read_only) {
+  ASSERT(!embedder_allocated());
+
   VirtualMemory::Protection prot;
   if (read_only) {
     if (type_ == kExecutable) {
       prot = VirtualMemory::kReadExecute;
     } else {
       prot = VirtualMemory::kReadOnly;
     }
   } else {
     prot = VirtualMemory::kReadWrite;
   }
@@ skipping 941 matching lines @@
     first = &exec_pages_;
     tail = &exec_pages_tail_;
   } else {
     page->type_ = HeapPage::kReadOnlyData;
     first = &pages_;
     tail = &pages_tail_;
   }
   if (*first == NULL) {
     *first = page;
   } else {
+    if (is_executable && FLAG_write_protect_code) {
+      (*tail)->WriteProtect(false);
+    }
     (*tail)->set_next(page);
+    if (is_executable && FLAG_write_protect_code) {
+      (*tail)->WriteProtect(true);
+    }
   }
   (*tail) = page;
 }
 
 
 PageSpaceController::PageSpaceController(Heap* heap,
                                          int heap_growth_ratio,
                                          int heap_growth_max,
                                          int garbage_collection_time_ratio)
     : heap_(heap),
@@ skipping 147 matching lines @@
     return 0;
   } else {
     ASSERT(total_time >= gc_time);
     int result = static_cast<int>(
         (static_cast<double>(gc_time) / static_cast<double>(total_time)) * 100);
     return result;
   }
 }
 
 }  // namespace dart