Remove clips where we can show that they are unnecessary.

Source/core/rendering/RenderBlock.cpp

Index: Source/core/rendering/RenderBlock.cpp
diff --git a/Source/core/rendering/RenderBlock.cpp b/Source/core/rendering/RenderBlock.cpp
index e45654332c8c1a54d3280d5390b011419c0901f5..b5fa26bba1e7e65404fccdd4ea168870d84adde2 100644
--- a/Source/core/rendering/RenderBlock.cpp
+++ b/Source/core/rendering/RenderBlock.cpp
@@ -1739,8 +1739,7 @@ void RenderBlock::addOverflowFromChildren()
         if (columnCount(colInfo)) {
             LayoutRect lastRect = columnRectAt(colInfo, columnCount(colInfo) - 1);
             addLayoutOverflow(lastRect);
-            if (!hasOverflowClip())
-                addVisualOverflow(lastRect);
+            addVisualOverflow(lastRect, VisualOverflowClippedByContentsClip);
         }
     }
 }
@@ -1778,7 +1777,7 @@ void RenderBlock::computeOverflow(LayoutUnit oldClientAfterEdge, bool recomputeF
     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);
+        addVisualOverflow(rectToApply, VisualOverflowClippedByContentsClip);
     }
 
     // Add visual overflow from box-shadow and border-image-outset.
@@ -1842,7 +1841,7 @@ void RenderBlock::addVisualOverflowFromTheme()
 
     IntRect inflatedRect = pixelSnappedBorderBoxRect();
     theme()->adjustRepaintRect(this, inflatedRect);
-    addVisualOverflow(inflatedRect);
+    addVisualOverflow(inflatedRect, VisualOverflowNotClipped);
 }
 
 bool RenderBlock::expandsToEncloseOverhangingFloats() const
@@ -2930,7 +2929,13 @@ void RenderBlock::paint(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
             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 = ContentsClipRequired;
+    if (hasOverflowClip() && !hasControlClip() && !(shouldPaintSelectionGaps() && phase == PaintPhaseForeground) && !hasCaret())
+        contentsClipBehavior = ContentsClipAutomatic;
+
+    bool pushedClip = pushContentsClip(paintInfo, adjustedPaintOffset, contentsClipBehavior);
     paintObject(paintInfo, adjustedPaintOffset);
     if (pushedClip)
         popContentsClip(paintInfo, phase, adjustedPaintOffset);
@@ -3123,8 +3128,7 @@ void RenderBlock::paintChild(RenderBox* child, PaintInfo& paintInfo, const Layou
         child->paint(paintInfo, childPoint);
 }
 
-
-void RenderBlock::paintCaret(PaintInfo& paintInfo, const LayoutPoint& paintOffset, CaretType type)
+bool RenderBlock::hasCaret(CaretType type)
 {
     // Paint the caret if the FrameSelection says so or if caret browsing is enabled
     bool caretBrowsing = frame()->settings() && frame()->settings()->caretBrowsingEnabled();
@@ -3137,13 +3141,18 @@ void RenderBlock::paintCaret(PaintInfo& paintInfo, const LayoutPoint& paintOffse
         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)