[MD] Don't use new OTR native-theming when using a custom browser theme.

chrome/browser/ui/views/dropdown_bar_host.cc

Index: chrome/browser/ui/views/dropdown_bar_host.cc
diff --git a/chrome/browser/ui/views/dropdown_bar_host.cc b/chrome/browser/ui/views/dropdown_bar_host.cc
index e2c408873f780c1be6d672bb84f0c2fc0ba01f5d..43f7a48ef85e937051f89e248af02b366547bc9d 100644
--- a/chrome/browser/ui/views/dropdown_bar_host.cc
+++ b/chrome/browser/ui/views/dropdown_bar_host.cc
@@ -17,6 +17,29 @@
 #include "ui/views/focus/view_storage.h"
 #include "ui/views/widget/widget.h"
 
+namespace {
+
+// TODO(estade): move this to its own file and reuse for

[Evan Stade, 2016/01/27 00:44:18]

I would complete this TODO before landing, but only if this general approach
lgty

+// OmniboxPopupContentsView::popup_.
+class ThemeCopyingWidget : public views::Widget {
+ public:
+  explicit ThemeCopyingWidget(views::Widget* role_model)
+      : role_model_(role_model) {}
+  ~ThemeCopyingWidget() override {}
+
+  const ui::NativeTheme* GetNativeTheme() const override {
+    return role_model_->GetNativeTheme();
+  }
+
+ private:
+  // The widget we'll copy our theme from.
+  views::Widget* role_model_;
+
+  DISALLOW_COPY_AND_ASSIGN(ThemeCopyingWidget);
+};
+
+}  // namespace
+
 // static
 bool DropdownBarHost::disable_animations_during_testing_ = false;
 
@@ -48,7 +71,7 @@ void DropdownBarHost::Init(views::View* host_view,
   delegate_ = delegate;
 
   // Initialize the host.
-  host_.reset(new views::Widget);
+  host_.reset(new ThemeCopyingWidget(browser_view_->GetWidget()));
   views::Widget::InitParams params(views::Widget::InitParams::TYPE_CONTROL);
   params.ownership = views::Widget::InitParams::WIDGET_OWNS_NATIVE_WIDGET;
   params.parent = browser_view_->GetWidget()->GetNativeView();