Revert "Mash: Protect virtualKeyboard events for null KeyboardController"

This reverts commit 2457438e.

Reason for revert: desktopui_MashLogin is still failing

Original change's description:
> Mash: Protect virtualKeyboard events for null KeyboardController
> 
> Currently the code is triggering a crash indesktopui_MashLogin:
> http://ubercautotest.corp.google.com/tko/retrieve_logs.cgi?job=/results/239691238-chromeos-test/chromeos4-row2-rack3-host12/debug/
> 
> Bug: 843332
> For extensions change:
> TBR=benwells@chromium.org
> 
> Change-Id: I51d94a6924407fffbb49994ff4cb02718b517866
> Reviewed-on: https://chromium-review.googlesource.com/1235206
> Commit-Queue: Steven Bennetts <stevenjb@chromium.org>
> Reviewed-by: James Cook <jamescook@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#592620}

TBR=jamescook@chromium.org,stevenjb@chromium.org

Change-Id: If44890c68926d991d4642fde4566408b6ce57fa0
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 843332
Reviewed-on: https://chromium-review.googlesource.com/1236837Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592852}

chrome/browser/extensions/api/virtual_keyboard_private/chrome_virtual_keyboard_delegate.cc

@@ -291,13 +291,7 @@ void ChromeVirtualKeyboardDelegate::OnHasInputDevices(
       "imeservice", base::FeatureList::IsEnabled(
                         chromeos::features::kImeServiceConnectable)));
 
-  keyboard::KeyboardController::KeyboardConfig config;
-  // KeyboardController::Get() may be null in Mash. TODO(stevenjb): Fix this.
-  // https://crbug.com/843332.
-  auto* keyboard_controller = keyboard::KeyboardController::Get();
-  if (keyboard_controller)
-    config = keyboard_controller->keyboard_config();
-
+  auto config = keyboard::KeyboardController::Get()->keyboard_config();
   // TODO(oka): Change this to use config.voice_input.
   features->AppendString(GenerateFeatureFlag(
       "voiceinput", has_audio_input_devices && config.voice_input &&