chromeos: use Env from Widget in TabStripDragController

This ensures the right Env is obtained.

BUG=847992
TEST=none

Change-Id: I5119cc7187c27fc6b5a38911777c974f12e3c093
Reviewed-on: https://chromium-review.googlesource.com/1181536Reviewed-by: Jun Mukai <mukai@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584505}

chrome/browser/ui/views/tabs/tab_drag_controller.cc

@@ -432,6 +432,10 @@ void TabDragController::Init(TabStrip* source_tabstrip,
   if (event_source == EVENT_SOURCE_TOUCH)
     source_tabstrip_->GetWidget()->SetCapture(source_tabstrip_);
 
+#if defined(USE_AURA)
+  env_ = source_tabstrip_->GetWidget()->GetNativeWindow()->env();
+#endif
+
 #if defined(OS_CHROMEOS)
   if (TabletModeClient::Get()->tablet_mode_enabled() &&
       !base::FeatureList::IsEnabled(ash::features::kDragTabsInTabletMode)) {
@@ -2003,8 +2007,7 @@ gfx::Point TabDragController::GetCursorScreenPoint() {
   // recognizer in mash until the mus side/window manager side RunMoveLoop() is
   // fixed to understand routing touch events. crbug.com/769507
   if (features::IsAshInBrowserProcess() &&
-      event_source_ == EVENT_SOURCE_TOUCH &&
-      aura::Env::GetInstance()->is_touch_down()) {
+      event_source_ == EVENT_SOURCE_TOUCH && env_->is_touch_down()) {
     views::Widget* widget = GetAttachedBrowserWidget();
     DCHECK(widget);
     aura::Window* widget_window = widget->GetNativeWindow();

chrome/browser/ui/views/tabs/tab_drag_controller.h

@@ -20,6 +20,12 @@
 #include "ui/gfx/native_widget_types.h"
 #include "ui/views/widget/widget_observer.h"
 
+#if defined(USE_AURA)
+namespace aura {
+class Env;
+}
+#endif
+
 namespace ui {
 class EventHandler;
 class ListSelectionModel;
@@ -497,10 +503,11 @@ class TabDragController : public views::WidgetObserver,
 
   EventSource event_source_;
 
-  // The TabStrip the drag originated from.
+  // The TabStrip the drag originated from. This is set to null if destroyed
+  // during the drag.
   TabStrip* source_tabstrip_;
 
-  // The TabStrip the dragged Tab is currently attached to, or NULL if the
+  // The TabStrip the dragged Tab is currently attached to, or null if the
   // dragged Tab is detached.
   TabStrip* attached_tabstrip_;
 
@@ -647,6 +654,10 @@ class TabDragController : public views::WidgetObserver,
 
   std::unique_ptr<WindowFinder> window_finder_;
 
+#if defined(USE_AURA)
+  aura::Env* env_ = nullptr;
+#endif
+
   base::WeakPtrFactory<TabDragController> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(TabDragController);