Fix dark mode detection in PasswordPendingView

Following discussion in crrev.com/c/1991710 about using dark mode PNGs,
the preferred approach is using color_utils::IsDark() instead of
GetNativeTheme()->ShouldUseDarkColors().

Change-Id: I50dceb05c8c902d148827b37914addf4e213c4d8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2019802
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735072}

chrome/browser/ui/views/passwords/password_pending_view.cc

@@ -28,6 +28,7 @@
 #include "ui/base/models/combobox_model_observer.h"
 #include "ui/base/models/simple_combobox_model.h"
 #include "ui/base/resource/resource_bundle.h"
+#include "ui/gfx/color_utils.h"
 #include "ui/gfx/paint_vector_icon.h"
 #include "ui/views/bubble/bubble_frame_view.h"
 #include "ui/views/controls/button/image_button.h"
@@ -422,7 +423,7 @@ void PasswordPendingView::AddedToWidget() {
 
 void PasswordPendingView::OnThemeChanged() {
   if (int id = model()->GetTopIllustration(
-          GetNativeTheme()->ShouldUseDarkColors())) {
+          color_utils::IsDark(GetBubbleFrameView()->GetBackgroundColor()))) {
     GetBubbleFrameView()->SetHeaderView(CreateHeaderImage(id));
   }
 }