Prime the landing pad for the new video rendering pipeline.

media/blink/video_frame_compositor.cc

Index: media/blink/video_frame_compositor.cc
diff --git a/media/blink/video_frame_compositor.cc b/media/blink/video_frame_compositor.cc
index 447b6b195bff674d3cb5ca2fd679ba0d59078d46..0f3737490474f43a2157a31996edd98b697b6f58 100644
--- a/media/blink/video_frame_compositor.cc
+++ b/media/blink/video_frame_compositor.cc
@@ -4,6 +4,8 @@
 
 #include "media/blink/video_frame_compositor.h"
 
+#include "base/bind.h"
+#include "base/message_loop/message_loop.h"
 #include "media/base/video_frame.h"
 
 namespace media {
@@ -32,35 +34,108 @@ static bool IsOpaque(const scoped_refptr<VideoFrame>& frame) {
 }
 
 VideoFrameCompositor::VideoFrameCompositor(
+    const scoped_refptr<base::SingleThreadTaskRunner>& compositor_task_runner,
     const base::Callback<void(gfx::Size)>& natural_size_changed_cb,
     const base::Callback<void(bool)>& opacity_changed_cb)
-    : natural_size_changed_cb_(natural_size_changed_cb),
+    : compositor_task_runner_(compositor_task_runner),
+      natural_size_changed_cb_(natural_size_changed_cb),
       opacity_changed_cb_(opacity_changed_cb),
-      client_(NULL) {
+      client_(nullptr),
+      callback_(nullptr),
+      rendering_(false) {
 }
 
 VideoFrameCompositor::~VideoFrameCompositor() {
+  DCHECK(compositor_task_runner_->BelongsToCurrentThread());
+  DCHECK(!callback_);
+  DCHECK(!rendering_);
   if (client_)
     client_->StopUsingProvider();
 }
 
+void VideoFrameCompositor::OnRendererStateUpdate() {
+  DCHECK(compositor_task_runner_->BelongsToCurrentThread());
+  if (!client_)
+    return;
+
+  base::AutoLock lock(lock_);
+  if (callback_) {
+    if (rendering_)
+      client_->StartRendering();
+
+    // TODO(dalecurtis): This will need to request the first frame so we have
+    // something to show, even if playback hasn't started yet.
+  } else if (rendering_) {
+    client_->StopRendering();
+  }
+}
+
+scoped_refptr<VideoFrame>
+VideoFrameCompositor::GetCurrentFrameAndUpdateIfStale() {
+  // TODO(dalecurtis): Implement frame refresh when stale.
+  DCHECK(compositor_task_runner_->BelongsToCurrentThread());
+  return GetCurrentFrame();
+}
+
 void VideoFrameCompositor::SetVideoFrameProviderClient(
     cc::VideoFrameProvider::Client* client) {
+  DCHECK(compositor_task_runner_->BelongsToCurrentThread());
   if (client_)
     client_->StopUsingProvider();
   client_ = client;
+  OnRendererStateUpdate();
 }
 
 scoped_refptr<VideoFrame> VideoFrameCompositor::GetCurrentFrame() {
+  DCHECK(compositor_task_runner_->BelongsToCurrentThread());
   return current_frame_;
 }
 
-void VideoFrameCompositor::PutCurrentFrame(
-    const scoped_refptr<VideoFrame>& frame) {
+void VideoFrameCompositor::PutCurrentFrame() {
+  DCHECK(compositor_task_runner_->BelongsToCurrentThread());
+  // TODO(dalecurtis): Wire up a flag for RenderCallback::OnFrameDropped().
 }
 
-void VideoFrameCompositor::UpdateCurrentFrame(
+bool VideoFrameCompositor::UpdateCurrentFrame(base::TimeTicks deadline_min,
+                                              base::TimeTicks deadline_max) {
+  // TODO(dalecurtis): Wire this up to RenderCallback::Render().
+  base::AutoLock lock(lock_);
+  return false;
+}
+
+void VideoFrameCompositor::Start(RenderCallback* callback) {
+  NOTREACHED();
+
+  // Called from the media thread.
+  base::AutoLock lock(lock_);
+  callback_ = callback;
+  rendering_ = true;
+  compositor_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&VideoFrameCompositor::OnRendererStateUpdate,
+                            base::Unretained(this)));

[xhwang, 2015/04/13 20:50:29]

Hmm, wondering why having both lock and post... If you bind callback_ and
rendering_ here, can you just drop the lock?

[DaleCurtis, 2015/04/13 23:15:06]

Because we need to ensure that callback_ is cleared before this function
returns, or an outstanding tick of the compositor could fire the callback before
this function returns.

[xhwang, 2015/04/14 00:29:52]

Thanks for the explanation! Maybe worth some comment here. It's not obvious now
since the callback_ is not used in UpdateCurrentFrame() yet.

+}
+
+void VideoFrameCompositor::Stop() {
+  NOTREACHED();
+
+  base::AutoLock lock(lock_);
+  callback_ = nullptr;
+  rendering_ = false;
+  compositor_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&VideoFrameCompositor::OnRendererStateUpdate,
+                            base::Unretained(this)));

[xhwang, 2015/04/13 20:50:29]

ditto

[DaleCurtis, 2015/04/13 23:15:06]

Acknowledged.

+}
+
+void VideoFrameCompositor::PaintFrameUsingOldRenderingPath(
     const scoped_refptr<VideoFrame>& frame) {
+  if (!compositor_task_runner_->BelongsToCurrentThread()) {
+    compositor_task_runner_->PostTask(
+        FROM_HERE,
+        base::Bind(&VideoFrameCompositor::PaintFrameUsingOldRenderingPath,
+                   base::Unretained(this), frame));
+    return;
+  }
+
   if (current_frame_.get() &&
       current_frame_->natural_size() != frame->natural_size()) {
     natural_size_changed_cb_.Run(frame->natural_size());