Replace hide-scrollbars flag with a web setting.

third_party/WebKit/Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 3337 matching lines @@
     // If the page's overflow setting has disabled scrolling, do not allow anything to override that setting.
     // http://crbug.com/426447
     LayoutObject* viewport = viewportLayoutObject();
     if (viewport && !shouldIgnoreOverflowHidden()) {
         if (viewport->style()->overflowX() == OverflowHidden)
             horizontalMode = ScrollbarAlwaysOff;
         if (viewport->style()->overflowY() == OverflowHidden)
             verticalMode = ScrollbarAlwaysOff;
     }
 
+    if (m_frame->settings() && m_frame->settings()->hideScrollbars()) {
+        horizontalMode = ScrollbarAlwaysOff;
+        verticalMode = ScrollbarAlwaysOff;
+    }
+
     if (horizontalMode != horizontalScrollbarMode() && !m_horizontalScrollbarLock) {
         m_horizontalScrollbarMode = horizontalMode;
         needsUpdate = true;
     }
 
     if (verticalMode != verticalScrollbarMode() && !m_verticalScrollbarLock) {
         m_verticalScrollbarMode = verticalMode;
         needsUpdate = true;
     }
 
@@ skipping 981 matching lines @@
 }
 
 bool FrameView::canThrottleRendering() const
 {
     if (!RuntimeEnabledFeatures::renderingPipelineThrottlingEnabled())
         return false;
     return m_subtreeThrottled || (m_hiddenForThrottling && m_crossOriginForThrottling);
 }
 
 } // namespace blink