Bug 1373739 - Disable WebGL in headless mode. r=bdahl

MozReview-Commit-ID: LWe9hRh7zXX

--HG--
extra : rebase_source : b97091b65b22e616fa6b99b819216b5b3f9c5b66

dom/canvas/WebGLContext.cpp

@@ -681,6 +681,15 @@ bool
 WebGLContext::CreateAndInitGL(bool forceEnabled,
                               std::vector<FailureReason>* const out_failReasons)
 {
+    // Can't use WebGL in headless mode.
+    if (gfxPlatform::IsHeadless()) {
+        FailureReason reason;
+        reason.info = "Can't use WebGL in headless mode (https://bugzil.la/1375585).";
+        out_failReasons->push_back(reason);
+        GenerateWarning("%s", reason.info.BeginReading());
+        return false;
+    }
+
     // WebGL2 is separately blocked:
     if (IsWebGL2()) {
         const nsCOMPtr<nsIGfxInfo> gfxInfo = services::GetGfxInfo();

testing/web-platform/tests/WebIDL/current-realm.html

@@ -110,8 +110,13 @@
      test(function() {
        var c = self[0].document.createElement("canvas"),
            obj = c.getContext(val)
-       assert_global(obj)
 
+       // WebGL might not be enabled in this environment
+       if (!obj && val === "webgl") {
+         return;
+       }
+
+       assert_global(obj)
        obj = HTMLCanvasElement.prototype.getContext.call(c, val)
        assert_global(obj)
      }, "getContext " + val)