Use RenderText directly to draw tooltip

ui/views/corewm/tooltip_aura.h

Index: ui/views/corewm/tooltip_aura.h
diff --git a/ui/views/corewm/tooltip_aura.h b/ui/views/corewm/tooltip_aura.h
index ce92fa25d151a77ab14ead3eb4576419ac133cb1..7343b903092dcdc0fca8d41b89dbbcd0cbdb3726 100644
--- a/ui/views/corewm/tooltip_aura.h
+++ b/ui/views/corewm/tooltip_aura.h
@@ -6,12 +6,12 @@
 #define UI_VIEWS_COREWM_TOOLTIP_AURA_H_
 
 #include "ui/gfx/screen_type_delegate.h"
-#include "ui/views/controls/label.h"
 #include "ui/views/corewm/tooltip.h"
 #include "ui/views/widget/widget_observer.h"
 
 namespace gfx {
 class FontList;
+class Size;
 }  // namespace gfx
 
 namespace views {
@@ -26,17 +26,9 @@ class VIEWS_EXPORT TooltipAura : public Tooltip, public WidgetObserver {
   TooltipAura();
   ~TooltipAura() override;
 
-  // Trims the tooltip to fit in the width |max_width|, setting |text| to the
-  // clipped result, |width| to the width (in pixels) of the clipped text
-  // and |line_count| to the number of lines of text in the tooltip. |font_list|
-  // is used to layout |text|. |max_width| comes from GetMaxWidth().
-  static void TrimTooltipToFit(const gfx::FontList& font_list,
-                               int max_width,
-                               base::string16* text,
-                               int* width,
-                               int* line_count);
-
  private:
+  class TooltipView;
+
   // Adjusts the bounds given by the arguments to fit inside the desktop
   // and applies the adjusted bounds to the label_.
   void SetTooltipBounds(const gfx::Point& mouse_pos,
@@ -58,8 +50,8 @@ class VIEWS_EXPORT TooltipAura : public Tooltip, public WidgetObserver {
   // WidgetObserver:
   void OnWidgetDestroying(Widget* widget) override;
 
-  // The label showing the tooltip.
-  Label label_;
+  // The view showing the tooltip.
+  TooltipView* tooltip_view_;
 
   // The widget containing the tooltip. May be NULL.
   Widget* widget_;