Route RTT texture updates through GL backend

src/canvas_layer.cpp

@@ -695,15 +695,11 @@ void LayerFrame::restore(const Snapshot& snap)
             // it's just a quick fix DON'T SHIP!!
             //m_rtt[i].recreate();
 
-            m_rtt[i].bindTexture();
             glm::vec2 box_sz = zw(m_dirty_box[i]) - xy(m_dirty_box[i]);
-            glTexSubImage2D(pp::renderer::gl::texture_2d_target(), 0,
+            m_rtt[i].updateRgba8(
                 static_cast<int>(m_dirty_box[i].x), static_cast<int>(m_dirty_box[i].y),
                 static_cast<int>(box_sz.x), static_cast<int>(box_sz.y),
-                pp::renderer::gl::rgba_pixel_format(),
-                pp::renderer::gl::unsigned_byte_component_type(),
                 snap.image[i].get());
-            m_rtt[i].unbindTexture();
             LOG("restore face %d - %d bytes (%dx%d)", i,
                 (int)box_sz.x * (int)box_sz.y * 4, (int)box_sz.x, (int)box_sz.y);
         }