views: Make view::Views::GetPreferredSize() const.

ash/popup_message.cc

Index: ash/popup_message.cc
diff --git a/ash/popup_message.cc b/ash/popup_message.cc
index f3217890a9e7b3e935d22e4bbaaf243b1a895ef6..b83ba9115703127291eed913ca5cea9edfbe7ed0 100644
--- a/ash/popup_message.cc
+++ b/ash/popup_message.cc
@@ -54,7 +54,7 @@ class PopupMessage::MessageBubble : public views::BubbleDelegateView {
 
  private:
   // views::View overrides:
-  virtual gfx::Size GetPreferredSize() OVERRIDE;
+  virtual gfx::Size GetPreferredSize() const OVERRIDE;
 
   // Each component (width/height) can force a size override for that component
   // if not 0.
@@ -163,7 +163,7 @@ void PopupMessage::MessageBubble::Close() {
     GetWidget()->Close();
 }
 
-gfx::Size PopupMessage::MessageBubble::GetPreferredSize() {
+gfx::Size PopupMessage::MessageBubble::GetPreferredSize() const {
   gfx::Size pref_size = views::BubbleDelegateView::GetPreferredSize();
   // Override the size with either the provided size or adjust it to not
   // violate our minimum / maximum sizes.