Capture Mode: use Env event handler

When ephemeral UI is present, capture mode was not handling events (such
as ENTER and ESC). This is based on the priority and order the event
handlers are added to the list. This CL bumps the priority up and uses
the Env event handler instead of the Shell one in order to move its
position higher up in the targets list.

Bug: 1166391
Test: manual
Change-Id: I3db050ff374ddb0883e88b197af81dcb4bd232ca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2715649
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Reviewed-by: Sammie Quon <sammiequon@chromium.org>
Commit-Queue: Richard Chui <richui@chromium.org>
Cr-Commit-Position: refs/heads/master@{#856962}

ash/capture_mode/capture_mode_session.cc

@@ -29,6 +29,7 @@
 #include "base/stl_util.h"
 #include "cc/paint/paint_flags.h"
 #include "ui/aura/client/capture_client.h"
+#include "ui/aura/env.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_tracker.h"
 #include "ui/base/cursor/cursor_factory.h"
@@ -551,7 +552,8 @@ CaptureModeSession::CaptureModeSession(CaptureModeController* controller)
   display::Screen::GetScreen()->AddObserver(this);
   // Our event handling code assumes the capture bar widget has been initialized
   // already. So we start handling events after everything has been setup.
-  Shell::Get()->AddPreTargetHandler(this);
+  aura::Env::GetInstance()->AddPreTargetHandler(
+      this, ui::EventTarget::Priority::kSystem);
 
   capture_mode_util::TriggerAccessibilityAlert(l10n_util::GetStringFUTF8(
       IDS_ASH_SCREEN_CAPTURE_ALERT_OPEN,
@@ -564,7 +566,7 @@ CaptureModeSession::CaptureModeSession(CaptureModeController* controller)
 }
 
 CaptureModeSession::~CaptureModeSession() {
-  Shell::Get()->RemovePreTargetHandler(this);
+  aura::Env::GetInstance()->RemovePreTargetHandler(this);
   display::Screen::GetScreen()->RemoveObserver(this);
   current_root_->RemoveObserver(this);
   TabletModeController::Get()->RemoveObserver(this);

ash/capture_mode/video_recording_watcher.cc

@@ -217,15 +217,15 @@ VideoRecordingWatcher::VideoRecordingWatcher(
 
   // Note the following:
   // 1- We add |this| as a pre-target handler of the |window_being_recorded_| as
-  //    opposed to |Shell|. This ensures that we only get mouse events when the
+  //    opposed to |Env|. This ensures that we only get mouse events when the
   //    window being recorded is the target. This is more efficient since we
   //    won't get any event when the curosr is in a different display, or
   //    targeting a different window.
-  // 2- We use the |kSystem| priority to ensure that we get these events before
-  //    other pre-target handlers can consume them (e.g. when opening a capture
-  //    mode session to take a screenshot while recording a video).
+  // 2- We use the |kAccessibility| priority to ensure that we get these events
+  //    before other pre-target handlers can consume them (e.g. when opening a
+  //    capture mode session to take a screenshot while recording a video).
   window_being_recorded_->AddPreTargetHandler(
-      this, ui::EventTarget::Priority::kSystem);
+      this, ui::EventTarget::Priority::kAccessibility);
 }
 
 VideoRecordingWatcher::~VideoRecordingWatcher() {