Remove GSC usage from ExynosVideoDecodeAccelerator.

cc/layers/video_layer_impl.cc

Index: cc/layers/video_layer_impl.cc
diff --git a/cc/layers/video_layer_impl.cc b/cc/layers/video_layer_impl.cc
index 28e470e7c3b698bcb736a9d52b20311c0c719ff1..b48b20f27422520046b6fd0f96e3927085715bdc 100644
--- a/cc/layers/video_layer_impl.cc
+++ b/cc/layers/video_layer_impl.cc
@@ -214,16 +214,16 @@ void VideoLayerImpl::AppendQuads(QuadSink* quad_sink,
       DCHECK_EQ(frame_resources_.size(), 1u);
       if (frame_resources_.size() < 1u)
         break;
-      gfx::Transform transform(
-          provider_client_impl_->stream_texture_matrix());
-      transform.Scale(tex_width_scale, tex_height_scale);
+      gfx::Transform scale;

[danakj, 2013/11/13 23:27:19]

I think the old code would be preferable.

This initializes an identity matrix, then scales it, then multiplies it.

The old code initializes a matrx from the stream texture, then scales it. Avoids
the identity step and the extra multiply.

[sheu, 2013/11/13 23:37:34]

Unfortunately, the two operations are not identical, which is why I had to put
this in :-(

What we need for sampling the stream texture is to do a stream texture transform
("T" matrix below), then a scale ("S" matrix below).  So:

  (u', v') = S * T * (u, v)

gfx::Transform::Scale() is a little backwards.  It has this comment:

  // Applies the current transformation on a scaling and assigns the result
  // to |this|.
  void Scale(SkMScalar x, SkMScalar y);

and does a SkMatrix44::preScale(), instead of an SkMatrix44::postScale().  So
what we get incorrectly is:

  (u', v') = T * S * (u, v)

It's a little confusing.

+      scale.Scale(tex_width_scale, tex_height_scale);
       scoped_ptr<StreamVideoDrawQuad> stream_video_quad =
           StreamVideoDrawQuad::Create();
-      stream_video_quad->SetNew(shared_quad_state,
-                                quad_rect,
-                                opaque_rect,
-                                frame_resources_[0],
-                                transform);
+      stream_video_quad->SetNew(
+          shared_quad_state,
+          quad_rect,
+          opaque_rect,
+          frame_resources_[0],
+          scale * provider_client_impl_->stream_texture_matrix());
       quad_sink->Append(stream_video_quad.PassAs<DrawQuad>(),
                         append_quads_data);
       break;