LabelButton: cache the last computed preferred size

ui/views/controls/button/label_button.h

Index: ui/views/controls/button/label_button.h
diff --git a/ui/views/controls/button/label_button.h b/ui/views/controls/button/label_button.h
index bceaf715654a99e288ae0f677d463a2c16a5d6de..5e730caaf93196c6621f98a303029c7dbddc1f65 100644
--- a/ui/views/controls/button/label_button.h
+++ b/ui/views/controls/button/label_button.h
@@ -65,9 +65,9 @@ class VIEWS_EXPORT LabelButton : public CustomButton,
   gfx::HorizontalAlignment GetHorizontalAlignment() const;
   void SetHorizontalAlignment(gfx::HorizontalAlignment alignment);
 
-  // Call set_min_size(gfx::Size()) to clear the monotonically increasing size.
-  void set_min_size(const gfx::Size& min_size) { min_size_ = min_size; }
-  void set_max_size(const gfx::Size& max_size) { max_size_ = max_size; }
+  // Call SetMinSize(gfx::Size()) to clear the monotonically increasing size.
+  void SetMinSize(const gfx::Size& min_size);
+  void SetMaxSize(const gfx::Size& max_size);
 
   // Get or set the option to handle the return key; false by default.
   bool is_default() const { return is_default_; }
@@ -144,6 +144,10 @@ class VIEWS_EXPORT LabelButton : public CustomButton,
   virtual ui::NativeTheme::State GetForegroundThemeState(
       ui::NativeTheme::ExtraParams* params) const OVERRIDE;
 
+  // Resets |cached_preferred_size_| and marks |cached_preferred_size_valid_|
+  // as false.
+  void ResetCachedPreferredSize();
+
   // The image and label shown in the button.
   ImageView* image_;
   Label* label_;
@@ -164,6 +168,10 @@ class VIEWS_EXPORT LabelButton : public CustomButton,
   // |max_size_| may be set to clamp the preferred size.
   gfx::Size max_size_;
 
+  // Cache the last computed preferred size.
+  mutable gfx::Size cached_preferred_size_;
+  mutable bool cached_preferred_size_valid_;
+
   // Flag indicating default handling of the return key via an accelerator.
   // Whether or not the button appears or behaves as the default button in its
   // current context;