Bug 1049960 - WebGL generate invalid operation errors when copyTex[Sub]Image2D is called with a format that is not a subset of the FBO format. r=jgilbert

dom/canvas/WebGLFramebuffer.cpp

@@ -76,6 +76,26 @@ WebGLFramebuffer::Attachment::HasAlpha() const
     return FormatHasAlpha(format);
 }
 
+GLenum
+WebGLFramebuffer::GetFormatForAttachment(const WebGLFramebuffer::Attachment& attachment) const
+{
+    MOZ_ASSERT(attachment.IsDefined());
+    MOZ_ASSERT(attachment.Texture() || attachment.Renderbuffer());
+
+    if (attachment.Texture()) {
+        const WebGLTexture& tex = *attachment.Texture();
+        MOZ_ASSERT(tex.HasImageInfoAt(tex.Target(), 0));
+
+        const WebGLTexture::ImageInfo& imgInfo = tex.ImageInfoAt(tex.Target(), 0);
+        return imgInfo.WebGLFormat();
+    }
+
+    if (attachment.Renderbuffer())
+        return attachment.Renderbuffer()->InternalFormat();
+
+    return LOCAL_GL_NONE;
+}
+
 bool
 WebGLFramebuffer::Attachment::IsReadableFloat() const
 {