minidump: Change the ownership model

minidump/minidump_writable.h

Index: minidump/minidump_writable.h
diff --git a/minidump/minidump_writable.h b/minidump/minidump_writable.h
index ccace8c863c714e329f0da2ab0bee4623aa7ba83..cfababf95ab105f6b4657d3aa887da828650a0a1 100644
--- a/minidump/minidump_writable.h
+++ b/minidump/minidump_writable.h
@@ -133,7 +133,13 @@ class MinidumpWritable {
   static const size_t kInvalidSize;
 
   MinidumpWritable();
-  ~MinidumpWritable();
+
+  // This doesn’t really need to be virtual because nothing ever deletes a
+  // MinidumpWritable* through an interface pointer with that type, and this is
+  // guaranteed by being protected. Regardless, the style guide is somewhat
+  // insistent.
+  // http://google-styleguide.googlecode.com/svn/trunk/cppguide.html#Inheritance
+  virtual ~MinidumpWritable();
 
   //! \brief The state of the object.
   State state() const { return state_; }