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

runtime/vm/virtual_memory.h

 // 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.
 
 #ifndef RUNTIME_VM_VIRTUAL_MEMORY_H_
 #define RUNTIME_VM_VIRTUAL_MEMORY_H_
 
 #include "platform/utils.h"
 #include "vm/globals.h"
 #include "vm/memory_region.h"
@@ skipping 46 matching lines @@
   static bool InSamePage(uword address0, uword address1);
 
   // Truncate this virtual memory segment. If try_unmap is false, the
   // memory beyond the new end is still accessible, but will be returned
   // upon destruction.
   void Truncate(intptr_t new_size, bool try_unmap = true);
 
   // Commit a reserved memory area, so that the memory can be accessed.
   bool Commit(uword addr, intptr_t size, bool is_executable);
 
-  bool embedder_allocated() const { return embedder_allocated_; }
+  bool vm_owns_region() const { return vm_owns_region_; }
 
-  static VirtualMemory* ForExternalPage(void* pointer, uword size);
+  static VirtualMemory* ForImagePage(void* pointer, uword size);
 
  private:
   static VirtualMemory* ReserveInternal(intptr_t size);
 
   // Free a sub segment. On operating systems that support it this
   // can give back the virtual memory to the system. Returns true on success.
   static bool FreeSubSegment(int32_t handle, void* address, intptr_t size);
 
   // This constructor is only used internally when reserving new virtual spaces.
   // It does not reserve any virtual address space on its own.
   explicit VirtualMemory(const MemoryRegion& region, int32_t handle = 0)
       : region_(region.pointer(), region.size()),
         reserved_size_(region.size()),
         handle_(handle),
-        embedder_allocated_(false) {}
+        vm_owns_region_(true) {}
 
   MemoryRegion region_;
 
   // The size of the underlying reservation not yet given back to the OS.
   // Its start coincides with region_, but its size might not, due to Truncate.
   intptr_t reserved_size_;
 
   int32_t handle_;
 
   static uword page_size_;
 
-  // True for a region provided by the embedder.
-  bool embedder_allocated_;
+  // False for a part of a snapshot added directly to the Dart heap, which
+  // belongs to the the embedder and must not be deallocated or have its
+  // protection status changed by the VM.
+  bool vm_owns_region_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(VirtualMemory);
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_VIRTUAL_MEMORY_H_