Use a single file for app snapshots.

runtime/bin/file.h

Index: runtime/bin/file.h
diff --git a/runtime/bin/file.h b/runtime/bin/file.h
index 6b22793ec5a45626ca3d73e83ebb36fa766b2865..f586894a26916fa9f50050edcb5850d178f526b8 100644
--- a/runtime/bin/file.h
+++ b/runtime/bin/file.h
@@ -88,7 +88,8 @@ class File : public ReferenceCounted<File> {
 
   intptr_t GetFD();
 
-  void* MapExecutable(intptr_t* num_bytes);
+  void* MapReadOnly(int64_t position, int64_t length);
+  void* MapReadExecute(int64_t position, int64_t length);

[siva, 2016/10/12 20:37:33]

Instead of having two entry points would it make sense to have just one

enum MapType {
  kReadOnly = 0,
  kReadExecute = 1,
  kReadWrite = 2,
};
void* Map(int64_t position, int64_t length, MapType type);

[rmacnak, 2016/10/13 01:08:16]

Done.

 
   // Read/Write attempt to transfer num_bytes to/from buffer. It returns
   // the number of bytes read/written.