snapshot: Make destructors of interface classes public and virtual

snapshot/memory_snapshot.h

Index: snapshot/memory_snapshot.h
diff --git a/snapshot/memory_snapshot.h b/snapshot/memory_snapshot.h
index e7d831668944bcb7db08d9ebc48156c4559d2513..f00610812eec8160a9040e33fd70c6604f6c0cc9 100644
--- a/snapshot/memory_snapshot.h
+++ b/snapshot/memory_snapshot.h
@@ -32,6 +32,8 @@ class MemorySnapshot {
   //! data is read, it will be passed to a delegate method.
   class Delegate {
    public:
+    virtual ~Delegate() {}
+
     //! \brief Called by MemorySnapshot::Read() to provide data requested by a
     //!     call to that method.
     //!
@@ -43,11 +45,10 @@ class MemorySnapshot {
     //! \return `true` on success, `false` on failure. MemoryDelegate::Read()
     //!     will use this as its own return value.
     virtual bool MemorySnapshotDelegateRead(void* data, size_t size) = 0;
-
-   protected:
-    ~Delegate() {}
   };
 
+  virtual ~MemorySnapshot() {}
+
   //! \brief The base address of the memory snapshot in the snapshot process’
   //!     address space.
   virtual uint64_t Address() const = 0;
@@ -68,9 +69,6 @@ class MemorySnapshot {
   //!     Delegate::MemorySnapshotDelegateRead(), which should be `true` on
   //!     success and `false` on failure.
   virtual bool Read(Delegate* delegate) const = 0;
-
- protected:
-  ~MemorySnapshot() {}
 };
 
 }  // namespace crashpad