Add ability for Widgets to override the DefaultThemeProvider

ui/views/widget/widget.cc

Index: ui/views/widget/widget.cc
diff --git a/ui/views/widget/widget.cc b/ui/views/widget/widget.cc
index 280969a84e5e7d0067d1f10378dec9d6d15061fb..5a1a0d13207ac3a69848ac5e384e71f6372020f3 100644
--- a/ui/views/widget/widget.cc
+++ b/ui/views/widget/widget.cc
@@ -158,6 +158,7 @@ Widget::Widget()
     : native_widget_(NULL),
       widget_delegate_(NULL),
       non_client_view_(NULL),
+      theme_provider_(nullptr),
       dragged_view_(NULL),
       ownership_(InitParams::NATIVE_WIDGET_OWNS_WIDGET),
       is_secondary_widget_(true),
@@ -742,6 +743,8 @@ bool Widget::IsVisible() const {
 }
 
 ui::ThemeProvider* Widget::GetThemeProvider() const {
+  if (theme_provider_)
+    return theme_provider_;
   const Widget* root_widget = GetTopLevelWidget();
   if (root_widget && root_widget != this) {
     // Attempt to get the theme provider, and fall back to the default theme
@@ -757,6 +760,12 @@ ui::ThemeProvider* Widget::GetThemeProvider() const {
   return default_theme_provider_.get();
 }
 
+void Widget::SetThemeProvider(ui::ThemeProvider* theme_provider) {
+  theme_provider_ = theme_provider;

[sadrul, 2015/08/31 17:51:07]

If a Widget has a theme-provider, then there's no reason to create the
DefaultThemeProvider for the Widget in the first-place, right? So, would it make
sense to include an optional theme-provider in InitParams when initializaing the
Widget?

[jonross, 2015/09/01 13:44:30]

We would not need the DefaultThemeProvider if they are using an alternate theme.
I could move this to the InitParams instead, as long as it is fine having Init
params not owned by the Widget

+  if (non_client_view_)
+    non_client_view_->Layout();

[sadrul, 2015/08/31 17:51:07]

Should this just call ThemeChanged() instead? (the Views that want a re-layout
on theme-change should trigger that from OnThemeChanged() override)

+}
+
 const ui::NativeTheme* Widget::GetNativeTheme() const {
   return native_widget_->GetNativeTheme();
 }