Auto merge of #13309 - anholt:webgl-fbo-prep, r=emilio

webgl: FBO support preparation

<!-- Please describe your changes on the following line: -->
Sending this PR now so that we can get the webrender patches merged.  This is prep for the webgl-fbo series, with one small fix for some conformance tests.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

<!-- Either: -->
- [X] There are tests for these changes OR
- [ ] These changes do not require tests because _____

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/13309)
<!-- Reviewable:end -->

1 files changed, 7 insertions, 0 deletions

diff --git a/components/script/dom/webglframebuffer.rs b/components/script/dom/webglframebuffer.rs
index 6e426fa0969..cd212d644bf 100644
--- a/components/script/dom/webglframebuffer.rs
+++ b/components/script/dom/webglframebuffer.rs
@@ -5,6 +5,7 @@
 // https://www.khronos.org/registry/webgl/specs/latest/1.0/webgl.idl
 use canvas_traits::CanvasMsg;
 use dom::bindings::codegen::Bindings::WebGLFramebufferBinding;
+use dom::bindings::codegen::Bindings::WebGLRenderingContextBinding::WebGLRenderingContextConstants as constants;
 use dom::bindings::global::GlobalRef;
 use dom::bindings::js::Root;
 use dom::bindings::reflector::reflect_dom_object;
@@ -79,6 +80,12 @@ impl WebGLFramebuffer {
         self.is_deleted.get()
     }
 
+    pub fn check_status(&self) -> u32 {
+        // Until we build support for attaching renderbuffers or
+        // textures, all user FBOs are incomplete.
+        return constants::FRAMEBUFFER_UNSUPPORTED;
+    }
+
     pub fn target(&self) -> Option<u32> {
         self.target.get()
     }