Bug 1156629 - OpenGL core context deprecated default VAO. r=jgilbert

Create a VAO and attach it to the default object.

dom/canvas/WebGLContextValidate.cpp

@@ -1949,6 +1949,21 @@ WebGLContext::InitAndValidateGL()
     mDefaultVertexArray->mAttribs.SetLength(mGLMaxVertexAttribs);
     mBoundVertexArray = mDefaultVertexArray;
 
+    // OpenGL core profiles remove the default VAO object from version
+    // 4.0.0. We create a default VAO for all core profiles,
+    // regardless of version.
+    //
+    // GL Spec 4.0.0:
+    // (https://www.opengl.org/registry/doc/glspec40.core.20100311.pdf)
+    // in Section E.2.2 "Removed Features", pg 397: "[...] The default
+    // vertex array object (the name zero) is also deprecated. [...]"
+
+    if (gl->IsCoreProfile()) {
+        MakeContextCurrent();
+        mDefaultVertexArray->GenVertexArray();
+        mDefaultVertexArray->BindVertexArray();
+    }
+
     if (mLoseContextOnMemoryPressure)
         mContextObserver->RegisterMemoryPressureEvent();