Don't try to set context callback if the context failed to be created.

BUG=142047

Review URL: https://chromiumcodereview.appspot.com/10828298

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@151430 0039d316-1c4b-4281-b951-d872f2087c98

content/renderer/render_thread_impl.cc

@@ -795,6 +795,7 @@ RenderThreadImpl::GetGpuVDAContext3D() {
         WebGraphicsContext3DCommandBufferImpl::CreateOffscreenContext(
             this, WebKit::WebGraphicsContext3D::Attributes(),
             GURL("chrome://gpu/RenderThreadImpl::GetGpuVDAContext3D")));
+    if (gpu_vda_context3d_.get())
       gpu_vda_context3d_->setContextLostCallback(context_lost_cb_.get());
   }
   return gpu_vda_context3d_.get();