Don't call ICoreWindow::Activate

Apparently (?) unnecessary, and it sometimes hangs in that call.

This doesn't seem to help the 16s timeout (per tryjobs here), but
doesn't seem to hurt either, and I can run on a local VM this way
at least.

BUG=411147

Review URL: https://codereview.chromium.org/583443005

Cr-Commit-Position: refs/heads/master@{#295594}

win8/metro_driver/chrome_app_view_ash.cc

@@ -677,12 +677,6 @@ ChromeAppViewAsh::Run() {
   HRESULT hr = window_->get_Dispatcher(dispatcher.GetAddressOf());
   CheckHR(hr, "Dispatcher failed.");
 
-  hr = window_->Activate();
-  if (FAILED(hr)) {
-    DLOG(WARNING) << "activation failed hr=" << hr;
-    return hr;
-  }
-
   // Create the IPC channel IO thread. It needs to out-live the ChannelProxy.
   base::Thread io_thread("metro_IO_thread");
   base::Thread::Options options;