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

runtime/vm/virtual_memory.h

Index: runtime/vm/virtual_memory.h
diff --git a/runtime/vm/virtual_memory.h b/runtime/vm/virtual_memory.h
index baa714d96b116516249b0d52242fbd87b9e287ad..4a7ecd27b3d174c835b9024583d78ea972004ed8 100644
--- a/runtime/vm/virtual_memory.h
+++ b/runtime/vm/virtual_memory.h
@@ -64,9 +64,9 @@ class VirtualMemory {
   // 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);
@@ -81,7 +81,7 @@ class VirtualMemory {
       : region_(region.pointer(), region.size()),
         reserved_size_(region.size()),
         handle_(handle),
-        embedder_allocated_(false) {}
+        vm_owns_region_(true) {}
 
   MemoryRegion region_;
 
@@ -93,8 +93,10 @@ class VirtualMemory {
 
   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);
 };