--- a/dom/canvas/WebGLContextState.cpp
+++ b/dom/canvas/WebGLContextState.cpp
@@ -314,17 +314,17 @@ WebGLContext::GetParameter(JSContext* cx
         case LOCAL_GL_GREEN_BITS:
         case LOCAL_GL_BLUE_BITS:
         case LOCAL_GL_ALPHA_BITS:
         case LOCAL_GL_DEPTH_BITS:
         case LOCAL_GL_STENCIL_BITS: {
             const auto format = [&]() -> const webgl::FormatInfo* {
                 if (mBoundDrawFramebuffer) {
                     const auto& fb = *mBoundDrawFramebuffer;
-                    const auto& attachment = [&]() {
+                    const auto& attachment = [&]() -> const auto& {
                         switch (pname) {
                         case LOCAL_GL_DEPTH_BITS:
                             return fb.AnyDepthAttachment();
 
                         case LOCAL_GL_STENCIL_BITS:
                             return fb.AnyStencilAttachment();
 
                         default:

--- a/dom/canvas/WebGLFramebuffer.h
+++ b/dom/canvas/WebGLFramebuffer.h
@@ -33,27 +33,28 @@ namespace gl {
 
 class WebGLFBAttachPoint final
 {
     friend class WebGLFramebuffer;
 public:
     WebGLFramebuffer* const mFB;
     const GLenum mAttachmentPoint;
 
-protected:
+private:
     WebGLRefPtr<WebGLTexture> mTexturePtr;
     WebGLRefPtr<WebGLRenderbuffer> mRenderbufferPtr;
     TexImageTarget mTexImageTarget;
     GLint mTexImageLayer;
     uint32_t mTexImageLevel;
 
     ////
 
     WebGLFBAttachPoint();
     WebGLFBAttachPoint(WebGLFramebuffer* fb, GLenum attachmentPoint);
+    explicit WebGLFBAttachPoint(WebGLFBAttachPoint&) = default; // Make this private.
 
 public:
     ~WebGLFBAttachPoint();
 
     ////
 
     void Unlink();