Fix border radius on composited children.

third_party/WebKit/Source/platform/graphics/paint/DrawingRecorder.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 "platform/graphics/paint/DrawingRecorder.h"
 
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/graphics/paint/PaintController.h"
@@ skipping 64 matching lines @@
     m_context.restore();
 
   m_context.setInDrawingRecorder(false);
   DCHECK(m_displayItemPosition ==
          m_context.getPaintController().newDisplayItemList().size());
 #endif
 
   sk_sp<const SkPicture> picture = m_context.endRecording();
 
 #if DCHECK_IS_ON()
+  // The check for DisplayItem::kPaintPhaseMax works because kPaintPhaseMax is
+  // PaintPhase::PaintPhaseClippingMask. But we can't use the latter because
+  // it lives in core. The check is needed because a child that needs a clipping
+  // mask needs it regardless of whether the child itself draws content,
+  // and that mask's DrawingRecorder has a non-empty picture even if the child
+  // itself draws no content.
   if (!RuntimeEnabledFeatures::slimmingPaintStrictCullRectClippingEnabled() &&
       !m_context.getPaintController().isForSkPictureBuilder() &&
+      m_displayItemType !=

[chrishtr, 2016/12/09 23:09:34]

I thought about this and tried out a few alternatives for avoiding this
situation,
but could find nothing simple that would work better than the current
implementation
of painting masks.

However, rather than this method of avoiding an assert, I would like this one:

return false from paintedOutputOfObjectHasNoEffectRegardlessOfSize() if 
layer()->compositingState() == PaintsIntoOwnBacking.

[Stephen Chennney, 2016/12/12 19:18:03]

Done.

+          DisplayItem::paintPhaseToDrawingType(DisplayItem::kPaintPhaseMax) &&
       m_displayItemClient.paintedOutputOfObjectHasNoEffectRegardlessOfSize()) {
     DCHECK_EQ(0, picture->approximateOpCount())
         << m_displayItemClient.debugName();
   }
 #endif
 
   m_context.getPaintController().createAndAppend<DrawingDisplayItem>(
       m_displayItemClient, m_displayItemType, picture, m_knownToBeOpaque);
 }
 
 }  // namespace blink