media: Reject pending CDM promise during destruction.

media/base/cdm_promise.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_BASE_CDM_PROMISE_H_
 #define MEDIA_BASE_CDM_PROMISE_H_
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 81 matching lines @@
   // CdmPromise implementation.
   virtual void reject(MediaKeys::Exception exception_code,
                       uint32_t system_code,
                       const std::string& error_message) = 0;
 
   ResolveParameterType GetResolveParameterType() const override {
     return CdmPromiseTraits<T...>::kType;
   }
 
  protected:
+  bool IsPromiseSettled() const { return is_settled_; }
+
   // All implementations must call this method in resolve() and reject() methods
   // to indicate that the promise has been settled.
   void MarkPromiseSettled() {
     // Promise can only be settled once.
     DCHECK(!is_settled_);
     is_settled_ = true;
   }
 
+  void RejectPromiseOnDestruction() {

[ddorwin, 2016/02/26 17:29:28]

// Must be called by the concrete destructor if !IsPromiseSettled().

You might also comment why this has to be called rather than just implemented in
the destructor.

[xhwang, 2016/02/26 20:52:21]

Done.

+    DCHECK(!is_settled_);
+    std::string message =
+        "Unfulfilled promise rejected automatically during destruction.";
+    DVLOG(1) << message;
+    reject(MediaKeys::INVALID_STATE_ERROR, 0, message);
+    DCHECK(is_settled_);
+  }
+
  private:
   // Keep track of whether the promise has been resolved or rejected yet.
   bool is_settled_;
 
   DISALLOW_COPY_AND_ASSIGN(CdmPromiseTemplate);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_CDM_PROMISE_H_