media: Add OnHasAdditionalUsableKey() in MediaDrmBridge

When an addtional usable key is available, instead of notifying the
player immediately, post a task (OnHasAdditionalUsableKey()) to the
|task_runner_| to notify the player.

Since UpdateSession() also happens on |task_runner_|, this makes
sure that OnHasAdditionalUsableKey() must run after UpdateSession()
returns. This helps avoid tricky race conditions.

This implementation is more consistent with the spec:
https://www.w3.org/TR/encrypted-media/#update-key-statuses

6.6.2 Update Key Statuses

5. Queue a task to fire a simple event named keystatuseschange at the
    session.

6. Queue a task to run the Attempt to Resume Playback If Necessary
    algorithm on each of the media element(s) whose mediaKeys
    attribute is the MediaKeys object that created the session.

BUG=597892
TEST=Resume playback after session update works.

Review URL: https://codereview.chromium.org/1827343002

Cr-Commit-Position: refs/heads/master@{#383253}

2 files changed, 22 insertions, 3 deletions

diff --git a/media/base/android/media_drm_bridge.cc b/media/base/android/media_drm_bridge.cc
index f82d176..96821ae 100644
--- a/media/base/android/media_drm_bridge.cc
+++ b/media/base/android/media_drm_bridge.cc
@@ -346,6 +346,7 @@ scoped_refptr<MediaDrmBridge> MediaDrmBridge::CreateWithoutSessionSupport(
 void MediaDrmBridge::SetServerCertificate(
     const std::vector<uint8_t>& certificate,
     scoped_ptr<media::SimpleCdmPromise> promise) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
   DVLOG(2) << __FUNCTION__ << "(" << certificate.size() << " bytes)";
 
   DCHECK(!certificate.empty());
@@ -366,6 +367,7 @@ void MediaDrmBridge::CreateSessionAndGenerateRequest(
     media::EmeInitDataType init_data_type,
     const std::vector<uint8_t>& init_data,
     scoped_ptr<media::NewSessionCdmPromise> promise) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
   DVLOG(2) << __FUNCTION__;
 
   if (session_type != media::MediaKeys::TEMPORARY_SESSION) {
@@ -421,6 +423,7 @@ void MediaDrmBridge::LoadSession(
     SessionType session_type,
     const std::string& session_id,
     scoped_ptr<media::NewSessionCdmPromise> promise) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
   DVLOG(2) << __FUNCTION__;
 
   NOTIMPLEMENTED() << "EME persistent sessions not yet supported on Android.";
@@ -431,6 +434,7 @@ void MediaDrmBridge::UpdateSession(
     const std::string& session_id,
     const std::vector<uint8_t>& response,
     scoped_ptr<media::SimpleCdmPromise> promise) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
   DVLOG(2) << __FUNCTION__;
 
   JNIEnv* env = AttachCurrentThread();
@@ -446,6 +450,7 @@ void MediaDrmBridge::UpdateSession(
 
 void MediaDrmBridge::CloseSession(const std::string& session_id,
                                   scoped_ptr<media::SimpleCdmPromise> promise) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
   DVLOG(2) << __FUNCTION__;
 
   JNIEnv* env = AttachCurrentThread();
@@ -460,6 +465,7 @@ void MediaDrmBridge::CloseSession(const std::string& session_id,
 void MediaDrmBridge::RemoveSession(
     const std::string& session_id,
     scoped_ptr<media::SimpleCdmPromise> promise) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
   DVLOG(2) << __FUNCTION__;
 
   NOTIMPLEMENTED() << "EME persistent sessions not yet supported on Android.";
@@ -664,9 +670,6 @@ void MediaDrmBridge::OnSessionKeysChange(
     bool has_additional_usable_key) {
   DVLOG(2) << __FUNCTION__;
 
-  if (has_additional_usable_key)
-    player_tracker_.NotifyNewKey();
-
   CdmKeysInfo cdm_keys_info;
 
   size_t size = env->GetArrayLength(j_keys_info);
@@ -697,6 +700,12 @@ void MediaDrmBridge::OnSessionKeysChange(
       FROM_HERE,
       base::Bind(session_keys_change_cb_, AsString(env, j_session_id),
                  has_additional_usable_key, base::Passed(&cdm_keys_info)));
+
+  if (has_additional_usable_key) {
+    task_runner_->PostTask(FROM_HERE,
+                           base::Bind(&MediaDrmBridge::OnHasAdditionalUsableKey,
+                                      weak_factory_.GetWeakPtr()));
+  }
 }
 
 // According to MeidaDrm documentation [1], zero |expiry_time_ms| means the keys
@@ -887,4 +896,11 @@ void MediaDrmBridge::ProcessProvisionResponse(bool success,
                                                j_response.obj());
 }
 
+void MediaDrmBridge::OnHasAdditionalUsableKey() {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  DVLOG(1) << __FUNCTION__;
+
+  player_tracker_.NotifyNewKey();
+}
+
 }  // namespace media
diff --git a/media/base/android/media_drm_bridge.h b/media/base/android/media_drm_bridge.h
index 0a74fcd..8c31f89 100644
--- a/media/base/android/media_drm_bridge.h
+++ b/media/base/android/media_drm_bridge.h
@@ -288,6 +288,9 @@ class MEDIA_EXPORT MediaDrmBridge : public MediaKeys, public PlayerTracker {
   // Process the data received by provisioning server.
   void ProcessProvisionResponse(bool success, const std::string& response);
 
+  // Called on the |task_runner_| when there is additional usable key.
+  void OnHasAdditionalUsableKey();
+
   // UUID of the key system.
   std::vector<uint8_t> scheme_uuid_;