Added quick lock mechanism while in Touchview

ash/wm/power_button_controller.cc

Index: ash/wm/power_button_controller.cc
diff --git a/ash/wm/power_button_controller.cc b/ash/wm/power_button_controller.cc
index 6e96c651dc5ba2ea47d4f44015dd3d9b3559fe74..ffce5573adc026d4a906d1992d8d358c7872d457 100644
--- a/ash/wm/power_button_controller.cc
+++ b/ash/wm/power_button_controller.cc
@@ -13,6 +13,7 @@
 #include "base/command_line.h"
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/display/types/chromeos/display_snapshot.h"
+#include "ui/events/event_handler.h"
 #include "ui/wm/core/compound_event_filter.h"
 
 namespace ash {
@@ -21,6 +22,7 @@ PowerButtonController::PowerButtonController(
     LockStateController* controller)
     : power_button_down_(false),
       lock_button_down_(false),
+      volume_down_pressed_(false),
       brightness_is_zero_(false),
       internal_display_off_and_external_display_on_(false),
       has_legacy_power_button_(
@@ -29,12 +31,14 @@ PowerButtonController::PowerButtonController(
       controller_(controller) {
 #if defined(OS_CHROMEOS)
   Shell::GetInstance()->display_configurator()->AddObserver(this);
+  Shell::GetInstance()->PrependPreTargetHandler(this);
 #endif
 }
 
 PowerButtonController::~PowerButtonController() {
 #if defined(OS_CHROMEOS)
   Shell::GetInstance()->display_configurator()->RemoveObserver(this);
+  Shell::GetInstance()->RemovePreTargetHandler(this);
 #endif
 }
 
@@ -55,6 +59,12 @@ void PowerButtonController::OnPowerButtonEvent(
   if (brightness_is_zero_ && !internal_display_off_and_external_display_on_)
     return;
 
+  if (volume_down_pressed_ && down) {
+    Shell::GetInstance()->accelerator_controller()->PerformAction(
+        ash::TAKE_SCREENSHOT, ui::Accelerator());
+    return;
+  }
+
   const SessionStateDelegate* session_state_delegate =
       Shell::GetInstance()->session_state_delegate();
   if (has_legacy_power_button_) {
@@ -116,6 +126,13 @@ void PowerButtonController::OnLockButtonEvent(
     controller_->CancelLockAnimation();
 }
 
+void PowerButtonController::OnKeyEvent(ui::KeyEvent* event) {
+  if (event->key_code() == ui::VKEY_VOLUME_DOWN) {
+    volume_down_pressed_ = event->type() == ui::ET_KEY_PRESSED ||
+                           event->type() == ui::ET_TRANSLATED_KEY_PRESS;
+  }
+}
+
 #if defined(OS_CHROMEOS)
 void PowerButtonController::OnDisplayModeChanged(
     const ui::DisplayConfigurator::DisplayStateList& display_states) {