Fix Linux audio playback for short files

media/audio/linux/alsa_output.cc

Index: media/audio/linux/alsa_output.cc
diff --git a/media/audio/linux/alsa_output.cc b/media/audio/linux/alsa_output.cc
index d8e502cf7699b60b49c794be0faa2c289f8b0408..8c5762b643e1a92248acfde4cb64a7d827cd34b6 100644
--- a/media/audio/linux/alsa_output.cc
+++ b/media/audio/linux/alsa_output.cc
@@ -395,6 +395,14 @@ void AlsaPcmOutputStream::StartTask() {
     return;
   }
 
+  if (shared_data_.state() != kIsPlaying) {
+    return;
+  }
+
+  // Before starting, the buffer might have audio from previous user of this
+  // device.
+  buffer_->Clear();
+
   // When starting again, drop all packets in the device and prepare it again
   // incase we are restarting from a pause state and need to flush old data.
   int error = wrapper_->PcmDrop(playback_handle_);
@@ -538,6 +546,10 @@ void AlsaPcmOutputStream::WritePacket() {
     return;
   }
 
+  if (shared_data_.state() == kIsStopped) {
+    return;
+  }
+
   CHECK_EQ(buffer_->forward_bytes() % bytes_per_output_frame_, 0u);
 
   const uint8* buffer_data;
@@ -579,6 +591,14 @@ void AlsaPcmOutputStream::WritePacket() {
       // Seek forward in the buffer after we've written some data to ALSA.
       buffer_->Seek(frames_written * bytes_per_output_frame_);
     }
+  } else {
+    // If nothing left to write and playback hasn't started yet, start it now.
+    // This ensures that shorter sounds will still play.
+    if (playback_handle_ &&
+        (wrapper_->PcmState(playback_handle_) == SND_PCM_STATE_PREPARED) &&
+        GetCurrentDelay() > 0) {
+      wrapper_->PcmStart(playback_handle_);
+    }
   }
 }
 
@@ -589,6 +609,10 @@ void AlsaPcmOutputStream::WriteTask() {
     return;
   }
 
+  if (shared_data_.state() == kIsStopped) {
+    return;
+  }
+
   bool source_exhausted;
   BufferPacket(&source_exhausted);
   WritePacket();