diff --git a/externs/closure-compiler.js b/externs/closure-compiler.js
index <HASH>..<HASH> 100644
--- a/externs/closure-compiler.js
+++ b/externs/closure-compiler.js
@@ -30,3 +30,15 @@ Touch.prototype.webkitRadiusX;
 
 /** @type {number} */
 Touch.prototype.webkitRadiusY;
+
+
+
+/**
+ * @type {boolean}
+ */
+WebGLContextAttributes.prototype.preferLowPowerToHighPerformance;
+
+/**
+ * @type {boolean}
+ */
+WebGLContextAttributes.prototype.failIfMajorPerformanceCaveat;
Add two missing properties to extern of WebGLContextAttributes

To be removed when the closure-compiler is updated