Use active window to calculate ax bounds

- Initially ExoShellSurface has both focus and active state. But when
  user clicks something on Android window, ExoSurface becomes focused.
  We need to use ExoShellSurface to get the widget. This CL changes it
  to use active window instead of focused one.

  click maximize button. Confirm that Chrome doesn't crash.

Bug: 867199
Test: Enable S2S and open Play Store app. Focus on the search box and
Change-Id: I74e363e2ee91986966a97a12f7cdb5399721f6cf
Reviewed-on: https://chromium-review.googlesource.com/1183046Reviewed-by: David Tseng <dtseng@chromium.org>
Commit-Queue: Yuki Awano <yawano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584919}

chrome/browser/chromeos/arc/accessibility/ax_tree_source_arc.cc

@@ -450,9 +450,9 @@ void AXTreeSourceArc::SerializeNode(AXNodeInfoData* node,
   // - Root node must exist.
   // - Window where this tree is attached to need to be focused.
   if (root_id_ != -1 && wm_helper) {
-    aura::Window* focused_window =
-        is_notification_ ? nullptr : wm_helper->GetFocusedWindow();
-    const gfx::Rect& local_bounds = GetBounds(node, focused_window);
+    aura::Window* active_window =
+        is_notification_ ? nullptr : wm_helper->GetActiveWindow();
+    const gfx::Rect& local_bounds = GetBounds(node, active_window);
     out_data->location.SetRect(local_bounds.x(), local_bounds.y(),
                                local_bounds.width(), local_bounds.height());
   }
@@ -504,18 +504,18 @@ void AXTreeSourceArc::SerializeNode(AXNodeInfoData* node,
 }
 
 const gfx::Rect AXTreeSourceArc::GetBounds(AXNodeInfoData* node,
-                                           aura::Window* focused_window) const {
+                                           aura::Window* active_window) const {
   DCHECK_NE(root_id_, -1);
 
   gfx::Rect node_bounds = node->bounds_in_screen;
 
-  if (focused_window && node->id == root_id_) {
+  if (active_window && node->id == root_id_) {
     // Top level window returns its bounds in dip.
-    aura::Window* toplevel_window = focused_window->GetToplevelWindow();
+    aura::Window* toplevel_window = active_window->GetToplevelWindow();
     float scale = toplevel_window->layer()->device_scale_factor();
 
     views::Widget* widget =
-        views::Widget::GetWidgetForNativeView(focused_window);
+        views::Widget::GetWidgetForNativeView(active_window);
     DCHECK(widget);
     DCHECK(widget->widget_delegate());
     DCHECK(widget->widget_delegate()->GetContentsView());