media: Reject pending CDM promise during destruction.

media/blink/cdm_result_promise.h

Index: media/blink/cdm_result_promise.h
diff --git a/media/blink/cdm_result_promise.h b/media/blink/cdm_result_promise.h
index 179654eae88a36ef7228b1f08c495bbc11f25cb4..c59d2c3990c16cc667ae3ba4ca4b4b77ba80f3af 100644
--- a/media/blink/cdm_result_promise.h
+++ b/media/blink/cdm_result_promise.h
@@ -56,6 +56,13 @@ CdmResultPromise<T...>::CdmResultPromise(
 
 template <typename... T>
 CdmResultPromise<T...>::~CdmResultPromise() {
+  if (web_cdm_result_.isCompleted())
+    return;
+
+  std::string message =
+      "Unfulfilled promise rejected automatically during destruction.";
+  DVLOG(1) << message;
+  reject(MediaKeys::INVALID_STATE_ERROR, 0, message);
 }
 
 // "inline" is needed to prevent multiple definition error.