Rename references to "external pages" as "snapshot pages" to avoid confusion with the kind of exter…

runtime/vm/gc_sweeper.cc

 // Copyright (c) 2011, 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/gc_sweeper.h"
 
 #include "vm/freelist.h"
 #include "vm/globals.h"
 #include "vm/heap.h"
 #include "vm/lockers.h"
 #include "vm/pages.h"
 #include "vm/safepoint.h"
 #include "vm/thread_pool.h"
 #include "vm/timeline.h"
 
 namespace dart {
 
 bool GCSweeper::SweepPage(HeapPage* page, FreeList* freelist, bool locked) {
-  if (page->embedder_allocated()) {
+  if (page->is_image_page()) {
     // Don't clear mark bits.
     return true;
   }
 
   // Keep track whether this page is still in use.
   bool in_use = false;
 
   bool is_executable = (page->type() == HeapPage::kExecutable);
   uword start = page->object_start();
   uword end = page->object_end();
@@ skipping 143 matching lines @@
                                 HeapPage* first,
                                 HeapPage* last,
                                 FreeList* freelist) {
   SweeperTask* task = new SweeperTask(isolate, isolate->heap()->old_space(),
                                       first, last, freelist);
   ThreadPool* pool = Dart::thread_pool();
   pool->Run(task);
 }
 
 }  // namespace dart