Revert of Remove FOUC avoidance from BlockPainter and DeprecatedPaintLayerPainter.

Source/core/paint/BlockPainter.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/paint/BlockPainter.h"
 
 #include "core/editing/DragCaretController.h"
 #include "core/editing/FrameSelection.h"
 #include "core/frame/Settings.h"
@@ skipping 272 matching lines @@
 
 bool BlockPainter::hasCaret() const
 {
     LocalFrame* frame = m_layoutBlock.frame();
     return hasCursorCaret(frame->selection(), &m_layoutBlock, frame)
         || hasDragCaret(frame->page()->dragCaretController(), &m_layoutBlock, frame);
 }
 
 void BlockPainter::paintContents(const PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
+    // Avoid painting descendants of the root element when stylesheets haven't loaded. This eliminates FOUC.
+    // It's ok not to draw, because later on, when all the stylesheets do load, styleResolverChanged() on the Document
+    // will do a full paint invalidation.
+    if (m_layoutBlock.document().didLayoutWithPendingStylesheets() && !m_layoutBlock.isLayoutView())
+        return;
+
     if (m_layoutBlock.childrenInline()) {
         LineBoxListPainter(*m_layoutBlock.lineBoxes()).paint(&m_layoutBlock, paintInfo, paintOffset);
     } else {
         PaintPhase newPhase = (paintInfo.phase == PaintPhaseChildOutlines) ? PaintPhaseOutline : paintInfo.phase;
         newPhase = (newPhase == PaintPhaseChildBlockBackgrounds) ? PaintPhaseChildBlockBackground : newPhase;
 
         // We don't paint our own background, but we do let the kids paint their backgrounds.
         PaintInfo paintInfoForChild(paintInfo);
         paintInfoForChild.phase = newPhase;
         paintInfoForChild.updatePaintingRootForChildren(&m_layoutBlock);
@@ skipping 45 matching lines @@
         LayoutBlock* block = flow->containingBlock();
         for ( ; block && block != &m_layoutBlock; block = block->containingBlock())
             accumulatedPaintOffset.moveBy(block->location());
         ASSERT(block);
         InlinePainter(*flow).paintOutline(info, accumulatedPaintOffset);
     }
 }
 
 
 } // namespace blink