Fix webrtc HW encode deadlock scenarios.

content/renderer/media/renderer_gpu_video_accelerator_factories.h

Index: content/renderer/media/renderer_gpu_video_accelerator_factories.h
diff --git a/content/renderer/media/renderer_gpu_video_accelerator_factories.h b/content/renderer/media/renderer_gpu_video_accelerator_factories.h
index fcc4ffb411a961b5968b135a7590d3efe1e40c95..4dcf4485be97eba3b94de5b0e9f9c1d1d61bb085 100644
--- a/content/renderer/media/renderer_gpu_video_accelerator_factories.h
+++ b/content/renderer/media/renderer_gpu_video_accelerator_factories.h
@@ -11,6 +11,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/synchronization/waitable_event.h"
+#include "base/threading/thread.h"
 #include "content/common/content_export.h"
 #include "media/filters/gpu_video_accelerator_factories.h"
 #include "third_party/skia/include/core/SkBitmap.h"
@@ -141,6 +142,17 @@ class CONTENT_EXPORT RendererGpuVideoAcceleratorFactories
   std::vector<uint32> created_textures_;
   std::vector<gpu::Mailbox> created_texture_mailboxes_;
 
+  // Renderer thread designated solely to allocate shared memory on. We hide on
+  // it from webrtc to avoid all kinds of deadlocks of varying complexity, which
+  // we would randomly end up in if we wanted to allocate shared memory on the
+  // renderer's ChildThread, as webrtc likes to sleep on it while calling into
+  // encoder via a varying number of indirections and/or while holding critical
+  // sections.
+  // The thread is owned by the original factories, while the proxy is shared
+  // by all clones.
+  scoped_ptr<base::Thread> shm_alloc_thread_;

[Ami GONE FROM CHROMIUM, 2013/09/04 20:47:56]

Previously you said that "the original factories only, which are in the
RenderThreadImpl" but AFAICT RTI::GetGpuFactories doesn't retain a ref to the
Factories it returns, so I don't understand what keeps the original Factories
alive (and thus the shm_alloc_thread_) for the lifetime of Clone()'d Factories.

+  scoped_refptr<base::MessageLoopProxy> shm_alloc_message_loop_;
+
   DISALLOW_COPY_AND_ASSIGN(RendererGpuVideoAcceleratorFactories);
 };