media: Reject pending CDM promise during destruction.

media/base/cdm_promise.h

Index: media/base/cdm_promise.h
diff --git a/media/base/cdm_promise.h b/media/base/cdm_promise.h
index 0c44f80c8fa19a19fcec0a1e79ba670ee4826478..6aeda5b7f4a8e9977717b31690a40c435b55037d 100644
--- a/media/base/cdm_promise.h
+++ b/media/base/cdm_promise.h
@@ -99,6 +99,8 @@ class MEDIA_EXPORT CdmPromiseTemplate : public CdmPromise {
   }
 
  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() {
@@ -107,6 +109,15 @@ class MEDIA_EXPORT CdmPromiseTemplate : public CdmPromise {
     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_;