Testbed classes inherit from oemcrypto reference code

Merge from Widevine repo of http://go/wvgerrit/58200

This CL removes code from the testbed that is duplicated in the
reference code using inheritance.

bug: 76393338 Split mock into reference code and testbed code
test: unit tests
Change-Id: I7b5f5330a595fa1756e6dfdf75bc07addb6107a8

libwvdrmengine/oemcrypto/ref/src/oemcrypto_scoped_ptr.h

@@ -20,6 +20,7 @@ class scoped_ptr {
  public:
   explicit scoped_ptr(T* p = NULL) : ptr_(p) {}
   T* get() const { return ptr_.get(); }
+  void reset(T* p = NULL) { ptr_.reset(p); }
 
  private:
   std::auto_ptr<T> ptr_;
@@ -35,7 +36,7 @@ class scoped_ptr {
   T& operator*() const { return *ptr_; }
   T* operator->() const { return ptr_.get(); }
   T* get() const { return ptr_.get(); }
-  void reset(T* p = NULL) { ptr_.reset(); }
+  void reset(T* p = NULL) { ptr_.reset(p); }
 
  private:
   std::unique_ptr<T> ptr_;