Allow the user to cancel the capture region action, and show its active status in the tray.

ash/utility/screenshot_controller_unittest.cc

 // Copyright 2014 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/utility/screenshot_controller.h"
 
 #include "ash/display/cursor_window_controller.h"
 #include "ash/display/mouse_cursor_event_filter.h"
 #include "ash/display/window_tree_host_manager.h"
 #include "ash/screenshot_delegate.h"
@@ skipping 29 matching lines @@
   void StartPartialScreenshotSession() {
     screenshot_controller()->StartPartialScreenshotSession(
         GetScreenshotDelegate(), true);
   }
 
   void StartWindowScreenshotSession() {
     screenshot_controller()->StartWindowScreenshotSession(
         GetScreenshotDelegate());
   }
 
-  void Cancel() { screenshot_controller()->Cancel(); }
+  void Cancel() { screenshot_controller()->CancelScreenshotSession(); }
 
   bool IsActive() {
     return screenshot_controller()->screenshot_delegate_ != nullptr;
   }
 
   const gfx::Point& GetStartPosition() const {
     return Shell::GetInstance()->screenshot_controller()->start_position_;
   }
 
   const aura::Window* GetCurrentSelectedWindow() const {
@@ skipping 414 matching lines @@
   EXPECT_FALSE(IsActive());
 
   StartWindowScreenshotSession();
   EXPECT_TRUE(IsActive());
   UpdateDisplay("400x400");
   RunAllPendingInMessageLoop();
   EXPECT_FALSE(IsActive());
 }
 
 }  // namespace ash