Move preferred scrollbar style preference change listening from renderer to browser, 1 of 3.

Source/web/mac/WebScrollbarTheme.cpp

Index: Source/web/mac/WebScrollbarTheme.cpp
diff --git a/Source/web/mac/WebScrollbarTheme.cpp b/Source/web/mac/WebScrollbarTheme.cpp
index 12228513766ab78fcf1d8e15fe2ed39a1e06a186..be04b7a0d1741839e0b92f946748c699b20a8b27 100644
--- a/Source/web/mac/WebScrollbarTheme.cpp
+++ b/Source/web/mac/WebScrollbarTheme.cpp
@@ -37,6 +37,11 @@ using namespace WebCore;
 
 namespace blink {
 
+#if defined(MAC_OS_X_VERSION_10_7) && MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_7
+COMPILE_ASSERT(ScrollerStyleLegacy == NSScrollerStyleLegacy, ScrollerStyle_Legacy_must_be_equal);
+COMPILE_ASSERT(ScrollerStyleOverlay == NSScrollerStyleOverlay, ScrollerStyle_Overlay_must_be_equal);
+#endif
+
 void WebScrollbarTheme::updateScrollbars(
     float initialButtonDelay, float autoscrollButtonDelay,
     bool jumpOnTrackClick, bool redraw)
@@ -49,4 +54,11 @@ void WebScrollbarTheme::updateScrollbars(
         initialButtonDelay, autoscrollButtonDelay, jumpOnTrackClick, redraw);
 }
 
+void WebScrollbarTheme::updateScrollbars(
+    float initialButtonDelay, float autoscrollButtonDelay,
+    bool jumpOnTrackClick, ScrollerStyle preferredScrollerStyle, bool redraw)
+{
+    updateScrollbars(initialButtonDelay, autoscrollButtonDelay, jumpOnTrackClick, redraw);
+}
+
 } // namespace blink