Add power-user keyboard mode for ChromeOS with Search key acting as a typical Fn key.

ash/accelerators/accelerator_controller.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/accelerators/accelerator_controller.h"
 
 #include <algorithm>
 #include <cmath>
 #include <string>
 
@@ skipping 516 matching lines @@
       return true;
     case TAKE_PARTIAL_SCREENSHOT:
       if (screenshot_delegate_.get()) {
         ash::PartialScreenshotView::StartPartialScreenshot(
             screenshot_delegate_.get());
       }
       // Return true to prevent propagation of the key event because
       // this key combination is reserved for partial screenshot.
       return true;
     case TOGGLE_APP_LIST:
+      // See: case NEXT_IME.
+      if (previous_event_type == ui::ET_KEY_RELEASED ||
+          // The LWIN binding is on release. If something else was pressed since
+          // the LWIN key, then we should ignore the release of LWIN.
+          (accelerator.type() == ui::ET_KEY_RELEASED &&
+           context_.previous_accelerator().key_code() != ui::VKEY_LWIN)) {
+        // We totally ignore this accelerator.
+        return false;
+      }
       if (key_code == ui::VKEY_LWIN && shell->delegate())
         shell->delegate()->RecordUserMetricsAction(UMA_ACCEL_SEARCH_LWIN);
       // When spoken feedback is enabled, we should neither toggle the list nor
       // consume the key since Search+Shift is one of the shortcuts the a11y
       // feature uses. crbug.com/132296
       DCHECK_EQ(ui::VKEY_LWIN, accelerator.key_code());
       if (Shell::GetInstance()->delegate()->IsSpokenFeedbackEnabled())
         return false;
       ash::Shell::GetInstance()->ToggleAppList();
       return true;
@@ skipping 322 matching lines @@
     keyboard_brightness_control_delegate) {
   keyboard_brightness_control_delegate_ =
       keyboard_brightness_control_delegate.Pass();
 }
 
 bool AcceleratorController::CanHandleAccelerators() const {
   return true;
 }
 
 }  // namespace ash