Fixed all unused-variable Clang warnings on Windows.

ui/views/window/custom_frame_view.cc

Index: ui/views/window/custom_frame_view.cc
diff --git a/ui/views/window/custom_frame_view.cc b/ui/views/window/custom_frame_view.cc
index 62a050764f9552d2661b9ed9d01e1d253ac61b43..d048ec87765875e608ad9aec9c0bb0e75cc6526f 100644
--- a/ui/views/window/custom_frame_view.cc
+++ b/ui/views/window/custom_frame_view.cc
@@ -48,13 +48,16 @@ const int kCaptionButtonHeightWithPadding = 19;
 const int kTitlebarTopAndBottomEdgeThickness = 2;
 // The icon is inset 2 px from the left frame border.
 const int kIconLeftSpacing = 2;
-// The icon never shrinks below 16 px on a side.
-const int kIconMinimumSize = 16;
 // The space between the window icon and the title text.
 const int kTitleIconOffsetX = 4;
 // The space between the title text and the caption buttons.
 const int kTitleCaptionSpacing = 5;
 
+#if !defined(OS_WIN)
+// The icon never shrinks below 16 px on a side.
+const int kIconMinimumSize = 16;
+#endif
+
 #if defined(OS_CHROMEOS)
 // Chrome OS uses a dark gray.
 const SkColor kDefaultColorFrame = SkColorSetRGB(109, 109, 109);