ash: Minor style guide fixes to //ash/accelerators

* Fix a couple of incorrect include guards.
* Use "return std::make_unique<T>(...)" instead of
  "return std::unique_ptr<T>(...)" because the latter is banned by a
  presubmit.

https://source.chromium.org/chromium/chromium/src/+/master:PRESUBMIT.py;drc=9c1f87c53ca0d29afdd5763b50cb26341ba1fd64;l=2596

I just noticed these incidentally while investigating another issue.

Bug: none
Change-Id: Id5ea994517ff41641a724cf0832da80f8ac7b680
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2530900
Commit-Queue: James Cook <jamescook@chromium.org>
Auto-Submit: James Cook <jamescook@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#826401}

ash/accelerators/accelerator_controller_impl.h

@@ -358,4 +358,4 @@ class ASH_EXPORT AcceleratorControllerImpl : public ui::AcceleratorTarget,
 
 }  // namespace ash
 
-#endif  // ASH_ACCELERATOR_CONTROLLER_IMPL_H_
+#endif  // ASH_ACCELERATORS_ACCELERATOR_CONTROLLER_IMPL_H_

ash/accelerators/key_hold_detector.h

@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef ASH_ACCELERATOR_KEY_HOLD_DETECTOR_H_
-#define ASH_ACCELERATOR_KEY_HOLD_DETECTOR_H_
+#ifndef ASH_ACCELERATORS_KEY_HOLD_DETECTOR_H_
+#define ASH_ACCELERATORS_KEY_HOLD_DETECTOR_H_
 
 #include <memory>
 
@@ -69,4 +69,4 @@ class ASH_EXPORT KeyHoldDetector : public ui::EventHandler {
 
 }  // namespace ash
 
-#endif  // ASH_ACCELERATOR_KEY_HOLD_DETECTOR_H_
+#endif  // ASH_ACCELERATORS_KEY_HOLD_DETECTOR_H_

ash/accelerators/magnifier_key_scroller.cc

@@ -35,10 +35,10 @@ void MagnifierKeyScroller::SetEnabled(bool enabled) {
 
 // static
 std::unique_ptr<ui::EventHandler> MagnifierKeyScroller::CreateHandler() {
+  // Uses `new` due to private constructor.
   std::unique_ptr<KeyHoldDetector::Delegate> delegate(
       new MagnifierKeyScroller());
-  return std::unique_ptr<ui::EventHandler>(
-      new KeyHoldDetector(std::move(delegate)));
+  return std::make_unique<KeyHoldDetector>(std::move(delegate));
 }
 
 bool MagnifierKeyScroller::ShouldProcessEvent(const ui::KeyEvent* event) const {

ash/accelerators/spoken_feedback_toggler.cc

@@ -28,10 +28,10 @@ void SpokenFeedbackToggler::SetEnabled(bool enabled) {
 
 // static
 std::unique_ptr<ui::EventHandler> SpokenFeedbackToggler::CreateHandler() {
+  // Uses `new` due to private constructor.
   std::unique_ptr<KeyHoldDetector::Delegate> delegate(
       new SpokenFeedbackToggler());
-  return std::unique_ptr<ui::EventHandler>(
-      new KeyHoldDetector(std::move(delegate)));
+  return std::make_unique<KeyHoldDetector>(std::move(delegate));
 }
 
 bool SpokenFeedbackToggler::ShouldProcessEvent(