Copy NV12 picture buffers on demand on the main thread.

third_party/khronos/EGL/eglext.h

Index: third_party/khronos/EGL/eglext.h
diff --git a/third_party/khronos/EGL/eglext.h b/third_party/khronos/EGL/eglext.h
index b6811a1eee3532eb0ad82a76dbc5dedc68ff6bc2..d07a7b730f66056d95d5d440920d531930cc507a 100644
--- a/third_party/khronos/EGL/eglext.h
+++ b/third_party/khronos/EGL/eglext.h
@@ -1214,6 +1214,32 @@ typedef EGLBoolean(EGLAPIENTRYP PFNGLEGLIMAGEFLUSHEXTERNALEXT)(
 #endif
 #endif
 
+#ifndef EGL_ANGLE_stream_producer_d3d_texture_nv12
+#define EGL_ANGLE_stream_producer_d3d_texture_nv12
+#define EGL_D3D_TEXTURE_SUBRESOURCE_ID_ANGLE 0x33AB
+typedef EGLBoolean(
+    EGLAPIENTRYP PFNEGLCREATESTREAMPRODUCERD3DTEXTURENV12ANGLEPROC)(
+    EGLDisplay dpy,
+    EGLStreamKHR stream,
+    const EGLAttrib* attrib_list);
+typedef EGLBoolean(EGLAPIENTRYP PFNEGLSTREAMPOSTD3DTEXTURENV12ANGLEPROC)(
+    EGLDisplay dpy,
+    EGLStreamKHR stream,
+    void* texture,
+    const EGLAttrib* attrib_list);
+#ifdef EGL_EGLEXT_PROTOTYPES
+EGLAPI EGLBoolean EGLAPIENTRY
+eglCreateStreamProducerD3DTextureNV12ANGLE(EGLDisplay dpy,
+                                           EGLStreamKHR stream,
+                                           const EGLAttrib* attrib_list);
+EGLAPI EGLBoolean EGLAPIENTRY
+eglStreamPostD3DTextureNV12ANGLE(EGLDisplay dpy,
+                                 EGLStreamKHR stream,
+                                 void* texture,
+                                 const EGLAttrib* attrib_list);
+#endif
+#endif
+
 #ifdef __cplusplus
 }
 #endif