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

Source/web/mac/WebScrollbarTheme.mm

Index: Source/web/mac/WebScrollbarTheme.mm
diff --git a/Source/web/mac/WebScrollbarTheme.mm b/Source/web/mac/WebScrollbarTheme.mm
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+/*
+ * Copyright (C) 2013 Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+#include "WebScrollbarTheme.h"
+
+#import <AppKit/AppKit.h>
+
+#include "platform/scroll/ScrollbarThemeMacCommon.h"
+#include "platform/mac/NSScrollerImpDetails.h"
+
+using namespace WebCore;
+
+namespace blink {
+
+COMPILE_ASSERT(ScrollerStyleLegacy == NSScrollerStyleLegacy, ScrollerStyle_Legacy_must_be_equal);
+COMPILE_ASSERT(ScrollerStyleOverlay == NSScrollerStyleOverlay, ScrollerStyle_Overlay_must_be_equal);
+
+void WebScrollbarTheme::updateScrollbars(
+    float initialButtonDelay, float autoscrollButtonDelay,
+    bool jumpOnTrackClick, ScrollerStyle preferredScrollerStyle, bool redraw)
+{
+    ScrollbarTheme* theme = ScrollbarTheme::theme();
+    if (theme->isMockTheme())
+        return;
+
+    static_cast<ScrollbarThemeMacCommon*>(ScrollbarTheme::theme())->preferencesChanged(
+        initialButtonDelay, autoscrollButtonDelay, jumpOnTrackClick, preferredScrollerStyle, redraw);
+}
+
+} // namespace blink