Bug 1496430 - Check GL context for RenderCompositorANGLE. r=sotaro

MozReview-Commit-ID: 7ncgoJOpZs9

Differential Revision: https://phabricator.services.mozilla.com/D7804

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

gfx/webrender_bindings/RenderCompositorANGLE.cpp

@@ -111,7 +111,10 @@ RenderCompositorANGLE::Initialize()
   if (!SutdownEGLLibraryIfNecessary()) {
     return false;
   }
-  RenderThread::Get()->SharedGL();
+  if (!RenderThread::Get()->SharedGL()) {
+    gfxCriticalNote << "[WR] failed to get shared GL context.";
+    return false;
+  }
 
   mDevice = GetDeviceOfEGLDisplay();