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

ash/shell/shell_delegate_impl.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/shell/shell_delegate_impl.h"
 
 #include "ash/app_list/app_list_presenter_delegate_factory.h"
 #include "ash/common/accessibility_delegate.h"
 #include "ash/common/default_accessibility_delegate.h"
 #include "ash/common/gpu_support_stub.h"
@@ skipping 80 matching lines @@
     return nullptr;
   }
   void CreateNote() override {}
   bool HasNoteApp() override { return false; }
   void SetPartialMagnifierState(bool enabled) override {}
   void SetStylusStateChangedCallback(
       const OnStylusStateChangedCallback& on_stylus_state_changed) override {}
   bool ShouldAutoOpenPalette() override { return false; }
   bool ShouldShowPalette() override { return false; }
   void TakeScreenshot() override {}
-  void TakePartialScreenshot() override {}
+  void TakePartialScreenshot(const base::Closure& done) override {}

[oshima, 2016/09/02 13:55:19]

nit: you may want to just run the callback for consistent behavior.

[jdufault, 2016/09/02 19:46:31]

Done.

+  void CancelPartialScreenshot() override {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(PaletteDelegateImpl);
 };
 
 class SessionStateDelegateImpl : public SessionStateDelegate {
  public:
   SessionStateDelegateImpl()
       : screen_locked_(false), user_info_(new user_manager::UserInfoImpl()) {}
 
@@ skipping 173 matching lines @@
 base::string16 ShellDelegateImpl::GetProductName() const {
   return base::string16();
 }
 
 gfx::Image ShellDelegateImpl::GetDeprecatedAcceleratorImage() const {
   return gfx::Image();
 }
 
 }  // namespace shell
 }  // namespace ash