Revert "Fixed Bubbles not tracking the NativeTheme of their anchoring Widget"

This reverts commit c939527d.

Reason for revert: regressed crbug.com/1065739

Original change's description:
> Fixed Bubbles not tracking the NativeTheme of their anchoring Widget
> 
> Currently child windows do not track the themes of their anchoring
> widget. This can lead to theme mismatches in spawned bubbles (in
> particular icons relying on native theme colors in the profile menu
> for linux themes).
> 
> This change follows on from a previous change that fixes the issue
> for ThemeProviders in Bubbles. Follow up CLs should address the
> issue for the more general case of widgets tracking the themes of
> the Widgets that spawned them (see https://crbug.com/948859).
> 
> Bug: 1057962
> Change-Id: Ie3a71208cb920e8bced6a8bb2f42968bad46f403
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2121075
> Commit-Queue: Thomas Lukaszewicz <tluk@chromium.org>
> Reviewed-by: Peter Kasting <pkasting@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#753398}

TBR=pkasting@chromium.org,tluk@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1057962
Change-Id: I16a9cae400f47ba2f5172637b8aefaea74050b3e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2131214Reviewed-by: Tim Song <tengs@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Thomas Lukaszewicz <tluk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#756031}

ui/views/bubble/bubble_dialog_delegate_view.cc

@@ -47,28 +47,15 @@ class BubbleWidget : public Widget {
   BubbleWidget() = default;
 
   // Widget:
-  // TODO(tluk) Fix child windows so that they inherit the theme properties of
-  // their parent. Currently this only fixes the problem for bubble dialogs
-  // anchored to another window. (https://crbug.com/948859)
   const ui::ThemeProvider* GetThemeProvider() const override {
-    const Widget* anchor_widget = GetAnchorWidget();
-    return anchor_widget ? anchor_widget->GetThemeProvider()
-                         : Widget::GetThemeProvider();
-  }
-
-  const ui::NativeTheme* GetNativeTheme() const override {
-    const Widget* anchor_widget = GetAnchorWidget();
-    return anchor_widget ? anchor_widget->GetNativeTheme()
-                         : Widget::GetNativeTheme();
-  }
-
- private:
-  const Widget* GetAnchorWidget() const {
     BubbleDialogDelegateView* const bubble_delegate =
         static_cast<BubbleDialogDelegateView*>(widget_delegate());
-    return bubble_delegate ? bubble_delegate->anchor_widget() : nullptr;
+    if (!bubble_delegate || !bubble_delegate->anchor_widget())
+      return Widget::GetThemeProvider();
+    return bubble_delegate->anchor_widget()->GetThemeProvider();
   }
 
+ private:
   DISALLOW_COPY_AND_ASSIGN(BubbleWidget);
 };