webgl: Unbind deleted objects from the GL side, not just our side.

Once FBOs are allowed, we were running into testcases that deleted the
active FBO, and expected the following ReadPixels to come from the
default framebuffer.

components/script/dom/webglrenderingcontext.rs

@@ -74,11 +74,17 @@ macro_rules! handle_potential_webgl_error {
 //
 // and similar text occurs for other object types.
 macro_rules! handle_object_deletion {
-    ($binding:expr, $object:ident) => {
+    ($self_:expr, $binding:expr, $object:ident, $unbind_command:expr) => {
         if let Some(bound_object) = $binding.get() {
             if bound_object.id() == $object.id() {
                 $binding.set(None);
             }
+
+            if let Some(command) = $unbind_command {
+                $self_.ipc_renderer
+                    .send(CanvasMsg::WebGL(command))
+                    .unwrap();
+            }
         }
     };
 }
@@ -1251,41 +1257,51 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.5
     fn DeleteBuffer(&self, buffer: Option<&WebGLBuffer>) {
         if let Some(buffer) = buffer {
-            handle_object_deletion!(self.bound_buffer_array, buffer);
-            handle_object_deletion!(self.bound_buffer_element_array, buffer);
+            handle_object_deletion!(self, self.bound_buffer_array, buffer,
+                                    Some(WebGLCommand::BindBuffer(constants::ARRAY_BUFFER, None)));
+            handle_object_deletion!(self, self.bound_buffer_element_array, buffer,
+                                    Some(WebGLCommand::BindBuffer(constants::ELEMENT_ARRAY_BUFFER, None)));
             buffer.delete()
         }
     }
 
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.6
     fn DeleteFramebuffer(&self, framebuffer: Option<&WebGLFramebuffer>) {
         if let Some(framebuffer) = framebuffer {
-            handle_object_deletion!(self.bound_framebuffer, framebuffer);
+            handle_object_deletion!(self, self.bound_framebuffer, framebuffer,
+                                    Some(WebGLCommand::BindFramebuffer(constants::FRAMEBUFFER,
+                                                                       WebGLFramebufferBindingRequest::Default)));
             framebuffer.delete()
         }
     }
 
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.7
     fn DeleteRenderbuffer(&self, renderbuffer: Option<&WebGLRenderbuffer>) {
         if let Some(renderbuffer) = renderbuffer {
-            handle_object_deletion!(self.bound_renderbuffer, renderbuffer);
+            handle_object_deletion!(self, self.bound_renderbuffer, renderbuffer,
+                                    Some(WebGLCommand::BindRenderbuffer(constants::RENDERBUFFER, None)));
             renderbuffer.delete()
         }
     }
 
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.8
     fn DeleteTexture(&self, texture: Option<&WebGLTexture>) {
         if let Some(texture) = texture {
-            handle_object_deletion!(self.bound_texture_2d, texture);
-            handle_object_deletion!(self.bound_texture_cube_map, texture);
+            handle_object_deletion!(self, self.bound_texture_2d, texture,
+                                    Some(WebGLCommand::BindTexture(constants::TEXTURE_2D, None)));
+            handle_object_deletion!(self, self.bound_texture_cube_map, texture,
+                                    Some(WebGLCommand::BindTexture(constants::TEXTURE_CUBE_MAP, None)));
             texture.delete()
         }
     }
 
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.9
     fn DeleteProgram(&self, program: Option<&WebGLProgram>) {
         if let Some(program) = program {
-            handle_object_deletion!(self.current_program, program);
+            // FIXME: We should call glUseProgram(0), but
+            // WebGLCommand::UseProgram() doesn't take an Option
+            // currently.  This is also a problem for useProgram(null)
+            handle_object_deletion!(self, self.current_program, program, None);
             program.delete()
         }
     }