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

runtime/vm/virtual_memory.cc

Index: runtime/vm/virtual_memory.cc
diff --git a/runtime/vm/virtual_memory.cc b/runtime/vm/virtual_memory.cc
index 93e3b84e08c8c17ec6baaeab7ed9482abadd43d3..38bb4b3fd37b118208914a2ba21586b30df01ef0 100644
--- a/runtime/vm/virtual_memory.cc
+++ b/runtime/vm/virtual_memory.cc
@@ -28,12 +28,12 @@ void VirtualMemory::Truncate(intptr_t new_size, bool try_unmap) {
 }
 
 
-VirtualMemory* VirtualMemory::ForExternalPage(void* pointer, uword size) {
+VirtualMemory* VirtualMemory::ForImagePage(void* pointer, uword size) {
   // Memory for precompilated instructions was allocated by the embedder, so
   // create a VirtualMemory without allocating.
   MemoryRegion region(pointer, size);
   VirtualMemory* memory = new VirtualMemory(region);
-  memory->embedder_allocated_ = true;
+  memory->vm_owns_region_ = false;
   return memory;
 }