Add more checks in MojoCdmService

This is to prevent abnormal cases from happening.

Bug: 999311
Test: Tested w/ shaka player demo and existing unit tests pass
Change-Id: Icef06d979351f16386cf3cbb177971a57a1e264c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1777139
Auto-Submit: Xiaohan Wang <xhwang@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: John Rummell <jrummell@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Xiaohan Wang <xhwang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#691911}

media/mojo/services/mojo_cdm_service.cc

@@ -60,7 +60,9 @@ void MojoCdmService::Initialize(const std::string& key_system,
                                 const CdmConfig& cdm_config,
                                 InitializeCallback callback) {
   DVLOG(1) << __func__ << ": " << key_system;
-  DCHECK(!cdm_);
+
+  CHECK(!has_initialize_been_called_) << "Initialize should only happen once";
+  has_initialize_been_called_ = true;
 
   auto weak_this = weak_factory_.GetWeakPtr();
   cdm_factory_->Create(
@@ -154,6 +156,7 @@ void MojoCdmService::OnCdmCreated(
     return;
   }
 
+  CHECK(!cdm_) << "CDM should only be created once.";
   cdm_ = cdm;
 
   if (context_) {

media/mojo/services/mojo_cdm_service.h

@@ -101,6 +101,8 @@ class MEDIA_MOJO_EXPORT MojoCdmService : public mojom::ContentDecryptionModule {
   // Callback for when |decryptor_| loses connectivity.
   void OnDecryptorConnectionError();
 
+  bool has_initialize_been_called_ = false;
+
   CdmFactory* cdm_factory_;
   MojoCdmServiceContext* const context_ = nullptr;
   scoped_refptr<::media::ContentDecryptionModule> cdm_;