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 4c569ff0f5b6346d61dd51bad499727400fe39d8..4c99d749788c9091ea7e5522f62679f33344f767 100644
--- a/ui/views/controls/button/label_button.h
+++ b/ui/views/controls/button/label_button.h
@@ -69,8 +69,14 @@ class VIEWS_EXPORT LabelButton : public CustomButton,
   void SetDirectionalityMode(gfx::DirectionalityMode mode);
 
   // 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; }
+  void set_min_size(const gfx::Size& min_size) {
+    min_size_ = min_size;
+    ResetCachedSize();
+  }
+  void set_max_size(const gfx::Size& max_size) {
+    max_size_ = max_size;
+    ResetCachedSize();
+  }
 
   // Get or set the option to handle the return key; false by default.
   bool is_default() const { return is_default_; }
@@ -146,6 +152,9 @@ class VIEWS_EXPORT LabelButton : public CustomButton,
   virtual ui::NativeTheme::State GetForegroundThemeState(
       ui::NativeTheme::ExtraParams* params) const OVERRIDE;
 
+  // Resets |button_size_| and marks |button_size_valid_| as false.
+  void ResetCachedSize();
+
   // The image and label shown in the button.
   ImageView* image_;
   Label* label_;
@@ -166,6 +175,10 @@ 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 button_size_;
+  mutable bool button_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;