Add the button style for combobox

ui/views/controls/button/label_button.cc

Index: ui/views/controls/button/label_button.cc
diff --git a/ui/views/controls/button/label_button.cc b/ui/views/controls/button/label_button.cc
index 243e92fffb7402f5acc6091b436ebadb416f5962..2d20f77eac66c4fc865e7fd94eae9c4ba1249b33 100644
--- a/ui/views/controls/button/label_button.cc
+++ b/ui/views/controls/button/label_button.cc
@@ -23,9 +23,6 @@ namespace {
 // The spacing between the icon and text.
 const int kSpacing = 5;
 
-// The length of the hover fade animation.
-const int kHoverAnimationDurationMs = 170;
-
 // Default text and shadow colors for STYLE_BUTTON.
 const SkColor kStyleButtonTextColor = SK_ColorBLACK;
 const SkColor kStyleButtonShadowColor = SK_ColorWHITE;
@@ -35,6 +32,9 @@ const SkColor kStyleButtonShadowColor = SK_ColorWHITE;
 namespace views {
 
 // static
+const int LabelButton::kHoverAnimationDurationMs = 170;
+
+// static
 const char LabelButton::kViewClassName[] = "LabelButton";
 
 LabelButton::LabelButton(ButtonListener* listener, const string16& text)