From b3e7a4b2a3230df5f00bc051216da509b28fc21a Mon Sep 17 00:00:00 2001
From: Bobby Holley <bobbyholley@gmail.com>
Date: Sat, 6 Jun 2015 15:00:36 -0700
Subject: [PATCH] Bug 1163223 - Use AwaitStartTime to invoke
 MediaDecoderReader::SetStartTime. r=jww

---
 dom/media/MediaDecoderReader.cpp       |  1 +
 dom/media/MediaDecoderReader.h         |  8 +++++++-
 dom/media/MediaDecoderStateMachine.cpp | 13 +++++++++----
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/dom/media/MediaDecoderReader.cpp b/dom/media/MediaDecoderReader.cpp
index 533237eafb6d..44e30512509a 100644
--- a/dom/media/MediaDecoderReader.cpp
+++ b/dom/media/MediaDecoderReader.cpp
@@ -148,6 +148,7 @@ void
 MediaDecoderReader::SetStartTime(int64_t aStartTime)
 {
   mDecoder->GetReentrantMonitor().AssertCurrentThreadIn();
+  MOZ_ASSERT(mStartTime == -1);
   mStartTime = aStartTime;
 }
 
diff --git a/dom/media/MediaDecoderReader.h b/dom/media/MediaDecoderReader.h
index 185bdae7cded..8513ed6d4788 100644
--- a/dom/media/MediaDecoderReader.h
+++ b/dom/media/MediaDecoderReader.h
@@ -328,7 +328,13 @@ protected:
   // The start time of the media, in microseconds. This is the presentation
   // time of the first frame decoded from the media. This is initialized to -1,
   // and then set to a value >= by MediaDecoderStateMachine::SetStartTime(),
-  // after which point it never changes.
+  // after which point it never changes (though SetStartTime may be called
+  // multiple times with the same value).
+  //
+  // This is an ugly breach of abstractions - it's currently necessary for the
+  // readers to return the correct value of GetBuffered. We should refactor
+  // things such that all GetBuffered calls go through the MDSM, which would
+  // offset the range accordingly.
   int64_t mStartTime;
 
   // This is a quick-and-dirty way for DecodeAudioData implementations to
diff --git a/dom/media/MediaDecoderStateMachine.cpp b/dom/media/MediaDecoderStateMachine.cpp
index 0a12972b28b9..f2b51fccde78 100644
--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -2177,6 +2177,15 @@ MediaDecoderStateMachine::OnMetadataRead(MetadataHolder* aMetadata)
   if (!mStartTimeRendezvous) {
     mStartTimeRendezvous = new StartTimeRendezvous(TaskQueue(), HasAudio(), HasVideo(),
                                                    mReader->ForceZeroStartTime() || IsRealTime());
+
+    mStartTimeRendezvous->AwaitStartTime()->Then(TaskQueue(), __func__,
+      [self] () -> void {
+        NS_ENSURE_TRUE_VOID(!self->IsShutdown());
+        ReentrantMonitorAutoEnter mon(self->mDecoder->GetReentrantMonitor());
+        self->mReader->SetStartTime(self->StartTime());
+      },
+      [] () -> void { NS_WARNING("Setting start time on reader failed"); }
+    );
   }
 
   if (mInfo.mMetadataDuration.isSome()) {
@@ -3176,10 +3185,6 @@ void MediaDecoderStateMachine::SetStartTime(int64_t aStartTimeUsecs)
     }
   }
 
-  // Pass along this immutable value to the reader so that it can make
-  // calculations independently of the state machine.
-  mReader->SetStartTime(mStartTime);
-
   // Set the audio start time to be start of media. If this lies before the
   // first actual audio frame we have, we'll inject silence during playback
   // to ensure the audio starts at the correct time.