Bug 1565365 - Let webgl.force-enabled apply to WebGL2 as well r=jgilbert

Differential Revision: https://phabricator.services.mozilla.com/D37821

--HG--
extra : moz-landing-system : lando

dom/canvas/WebGLContext.cpp

@@ -455,7 +455,7 @@ bool WebGLContext::CreateAndInitGL(
   }
 
   // WebGL2 is separately blocked:
-  if (IsWebGL2()) {
+  if (IsWebGL2() && !forceEnabled) {
     const nsCOMPtr<nsIGfxInfo> gfxInfo = services::GetGfxInfo();
     const auto feature = nsIGfxInfo::FEATURE_WEBGL2;