Ensure buffers are unbound at end of frame.

This fixes asserts in some software backends on shutdown.

webrender/src/device.rs

@@ -1608,6 +1608,13 @@ impl Device {
 
         gl::bind_texture(gl::TEXTURE_2D, 0);
         gl::use_program(0);
+
+        for i in 0..self.bound_textures.len() {
+            gl::active_texture(gl::TEXTURE0 + i as gl::GLuint);
+            gl::bind_texture(gl::TEXTURE_2D, 0);
+        }
+
+        gl::active_texture(gl::TEXTURE0);
     }
 }
 

webrender/src/renderer.rs

@@ -604,6 +604,10 @@ impl Renderer {
                     //self.update_shaders();
                     self.update_texture_cache();
                     self.draw_tile_frame(frame, &framebuffer_size);
+
+                    gl::bind_buffer(gl::UNIFORM_BUFFER, 0);
+                    gl::bind_buffer_base(gl::UNIFORM_BUFFER, UBO_BIND_DATA, 0);
+                    gl::bind_buffer_base(gl::UNIFORM_BUFFER, UBO_BIND_TILES, 0);
                 });
 
                 let current_time = precise_time_ns();