Remove clips where we can show that they are unnecessary.

Source/core/rendering/RenderBlock.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 1696 matching lines @@
     if (!hasColumns()) {
         if (childrenInline())
             addOverflowFromInlineChildren();
         else
             addOverflowFromBlockChildren();
     } else {
         ColumnInfo* colInfo = columnInfo();
         if (columnCount(colInfo)) {
             LayoutRect lastRect = columnRectAt(colInfo, columnCount(colInfo) - 1);
             addLayoutOverflow(lastRect);
-            if (!hasOverflowClip())
-                addVisualOverflow(lastRect);
+            addContentsVisualOverflow(lastRect);
         }
     }
 }
 
 void RenderBlock::computeOverflow(LayoutUnit oldClientAfterEdge, bool recomputeFloats)
 {
     m_overflow.clear();
 
     // Add overflow from children.
     addOverflowFromChildren();
@@ skipping 17 matching lines @@
         addLayoutOverflow(rectToApply);
         if (hasRenderOverflow())
             m_overflow->setLayoutClientAfterEdge(oldClientAfterEdge);
     }
 
     // Allow our overflow to catch cases where the caret in an empty editable element with negative text indent needs to get painted.
     LayoutUnit textIndent = textIndentOffset();
     if (textIndent < 0) {
         LayoutRect clientRect(noOverflowRect());
         LayoutRect rectToApply = LayoutRect(clientRect.x() + min<LayoutUnit>(0, textIndent), clientRect.y(), clientRect.width() - min<LayoutUnit>(0, textIndent), clientRect.height());
-        addVisualOverflow(rectToApply);
+        addContentsVisualOverflow(rectToApply);
     }
 
     // Add visual overflow from box-shadow and border-image-outset.
     addVisualEffectOverflow();
 
     // Add visual overflow from theme.
     addVisualOverflowFromTheme();
 
     if (isRenderNamedFlowThread())
         toRenderNamedFlowThread(this)->computeOversetStateForRegions(oldClientAfterEdge);
@@ skipping 1130 matching lines @@
     // paints the root's background.
     if (!isRoot()) {
         LayoutRect overflowBox = overflowRectForPaintRejection();
         flipForWritingMode(overflowBox);
         overflowBox.inflate(maximalOutlineSize(paintInfo.phase));
         overflowBox.moveBy(adjustedPaintOffset);
         if (!overflowBox.intersects(paintInfo.rect))
             return;
     }
 
-    bool pushedClip = pushContentsClip(paintInfo, adjustedPaintOffset);
+    // There are some cases where not all clipped visual overflow is accounted for.
+    // FIXME: reduce the number of such cases.
+    ContentsClipBehavior contentsClipBehavior = ForceContentsClip;
+    if (hasOverflowClip() && !hasControlClip() && !(shouldPaintSelectionGaps() && phase == PaintPhaseForeground) && !hasCaret())
+        contentsClipBehavior = SkipContentsClipIfPossible;
+
+    bool pushedClip = pushContentsClip(paintInfo, adjustedPaintOffset, contentsClipBehavior);
     paintObject(paintInfo, adjustedPaintOffset);
     if (pushedClip)
         popContentsClip(paintInfo, phase, adjustedPaintOffset);
 
     // Our scrollbar widgets paint exactly when we tell them to, so that they work properly with
     // z-index.  We paint after we painted the background/border, so that the scrollbars will
     // sit above the background/border.
     if (hasOverflowClip() && style()->visibility() == VISIBLE && (phase == PaintPhaseBlockBackground || phase == PaintPhaseChildBlockBackground) && paintInfo.shouldPaintWithinRoot(this) && !paintInfo.paintRootBackgroundOnly())
         layer()->paintOverflowControls(paintInfo.context, roundedIntPoint(adjustedPaintOffset), paintInfo.rect);
 }
@@ skipping 172 matching lines @@
         paintChild(child, paintInfo, paintOffset);
 }
 
 void RenderBlock::paintChild(RenderBox* child, PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     LayoutPoint childPoint = flipForWritingModeForChild(child, paintOffset);
     if (!child->hasSelfPaintingLayer() && !child->isFloating())
         child->paint(paintInfo, childPoint);
 }
 
-
-void RenderBlock::paintCaret(PaintInfo& paintInfo, const LayoutPoint& paintOffset, CaretType type)
+bool RenderBlock::hasCaret(CaretType type) const
 {
     // Paint the caret if the FrameSelection says so or if caret browsing is enabled
     bool caretBrowsing = frame()->settings() && frame()->settings()->caretBrowsingEnabled();
     RenderObject* caretPainter;
     bool isContentEditable;
     if (type == CursorCaret) {
         caretPainter = frame()->selection()->caretRenderer();
         isContentEditable = frame()->selection()->rendererIsEditable();
     } else {
         caretPainter = frame()->page()->dragCaretController()->caretRenderer();
         isContentEditable = frame()->page()->dragCaretController()->isContentEditable();
     }
+    return caretPainter == this && (isContentEditable || caretBrowsing);
+}
 
-    if (caretPainter == this && (isContentEditable || caretBrowsing)) {
-        if (type == CursorCaret)
-            frame()->selection()->paintCaret(paintInfo.context, paintOffset, paintInfo.rect);
-        else
-            frame()->page()->dragCaretController()->paintDragCaret(frame(), paintInfo.context, paintOffset, paintInfo.rect);
-    }
+void RenderBlock::paintCaret(PaintInfo& paintInfo, const LayoutPoint& paintOffset, CaretType type)
+{
+    if (!hasCaret(type))
+        return;
+
+    if (type == CursorCaret)
+        frame()->selection()->paintCaret(paintInfo.context, paintOffset, paintInfo.rect);
+    else
+        frame()->page()->dragCaretController()->paintDragCaret(frame(), paintInfo.context, paintOffset, paintInfo.rect);
 }
 
 void RenderBlock::paintObject(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     PaintPhase paintPhase = paintInfo.phase;
 
     // 1. paint background, borders etc
     if ((paintPhase == PaintPhaseBlockBackground || paintPhase == PaintPhaseChildBlockBackground) && style()->visibility() == VISIBLE) {
         if (hasBoxDecorations())
             paintBoxDecorations(paintInfo, paintOffset);
@@ skipping 5011 matching lines @@
 
 String ValueToString<RenderBlock::FloatingObject*>::string(const RenderBlock::FloatingObject* floatingObject)
 {
     return String::format("%p (%dx%d %dx%d)", floatingObject, floatingObject->frameRect().pixelSnappedX(), floatingObject->frameRect().pixelSnappedY(), floatingObject->frameRect().pixelSnappedMaxX(), floatingObject->frameRect().pixelSnappedMaxY());
 }
 
 
 #endif
 
 } // namespace WebCore