Enable new multicol for testing and experimental web platform features.

Source/core/layout/LayoutBlockFlow.cpp

 /*
  * 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
@@ skipping 34 matching lines @@
 #include "core/layout/LayoutText.h"
 #include "core/layout/LayoutView.h"
 #include "core/layout/TextAutosizer.h"
 #include "core/layout/line/LineBreaker.h"
 #include "core/layout/line/LineWidth.h"
 #include "core/paint/BlockFlowPainter.h"
 #include "core/paint/ClipScope.h"
 #include "core/paint/DeprecatedPaintLayer.h"
 #include "core/paint/LayoutObjectDrawingRecorder.h"
 #include "core/paint/PaintInfo.h"
+#include "platform/RuntimeEnabledFeatures.h"
 #include "platform/geometry/TransformState.h"
 #include "platform/text/BidiTextRun.h"
 
 namespace blink {
 
 bool LayoutBlockFlow::s_canPropagateFloatIntoSibling = false;
 
 struct SameSizeAsMarginInfo {
     uint16_t bitfields;
     LayoutUnit margins[2];
@@ skipping 3030 matching lines @@
         // Paged overflow is currently done using the multicol implementation.
         return LayoutPagedFlowThread::createAnonymous(document(), styleRef());
     default:
         ASSERT_NOT_REACHED();
         return nullptr;
     }
 }
 
 void LayoutBlockFlow::createOrDestroyMultiColumnFlowThreadIfNeeded(const ComputedStyle* oldStyle)
 {
-    if (!document().regionBasedColumnsEnabled())
+    if (!RuntimeEnabledFeatures::regionBasedColumnsEnabled())
         return;
 
     // Paged overflow trumps multicol in this implementation. Ideally, it should be possible to have
     // both paged overflow and multicol on the same element, but then we need two flow
     // threads. Anyway, this is nothing to worry about until we can actually nest multicol properly
     // inside other fragmentation contexts.
     FlowThreadType type = flowThreadType(styleRef());
 
     if (multiColumnFlowThread()) {
         ASSERT(oldStyle);
@@ skipping 68 matching lines @@
     FrameView* frameView = document().view();
     LayoutUnit top = (style()->position() == FixedPosition) ? 0 : frameView->scrollOffset().height();
     int visibleHeight = frameView->visibleContentRect(IncludeScrollbars).height();
     if (size().height() < visibleHeight)
         top += (visibleHeight - size().height()) / 2;
     setY(top);
     dialog->setCentered(top);
 }
 
 } // namespace blink