Removing a RenderLayer's CLM should trigger a repaint

Source/core/rendering/compositing/RenderLayerCompositor.cpp

 /*
  * Copyright (C) 2009, 2010 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
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@@ skipping 462 matching lines @@
         layer->setViewportConstrainedNotCompositedReason(viewportConstrainedNotCompositedReason);
         return true;
     }
     return false;
 }
 
 // These are temporary hacks to work around chicken-egg issues while we continue to refactor the compositing code.
 // See crbug.com/383191 for a list of tests that fail if this method is removed.
 void RenderLayerCompositor::applyUpdateLayerCompositingStateChickenEggHacks(RenderLayer* layer, CompositingStateTransitionType compositedLayerUpdate)
 {
-    if (compositedLayerUpdate != NoCompositingStateChange)
-        allocateOrClearCompositedLayerMapping(layer, compositedLayerUpdate);
+    if (compositedLayerUpdate != NoCompositingStateChange) {
+        bool compositedLayerMappingChanged = allocateOrClearCompositedLayerMapping(layer, compositedLayerUpdate);
+        if (compositedLayerMappingChanged) {
+            if (layer->parent())

[chrishtr, 2014/06/13 15:45:38]

Please add a comment here about why the layer->parent() part is here, as well as
why parent() will
always be non-null in cases when the layer is attached. We had no idea why the
old conditional was there,
which is why I removed it.

[ajuma, 2014/06/13 18:03:50]

Done.

+                layer->repainter().computeRepaintRectsIncludingNonCompositingDescendants();

[ajuma, 2014/06/13 14:54:52]

I also needed to make this call conditional on having a parent (matching the
logic that used to exist in allocateOrClearCompositedLayerMapping for the case
of allocating a new mapping) -- the chicken-egg compositing update can happen
before a RenderObject is added to the render tree (see the logic in
RenderTreeBuilder::createRendererForElementIfNeeded, where the compositing
update happens during the call to setStyle, which happens before the
RenderObject is added to its parent), but trying to compute repaint rects
without a parent leads to a crash in
RenderTableCell::clippedOverflowRectForRepaint, since this assumes a non-null
parent.

+            repaintOnCompositingChange(layer);
+        }
+    }
 }
 
 void RenderLayerCompositor::updateLayerCompositingState(RenderLayer* layer, UpdateLayerCompositingStateOptions options)
 {
     updateDirectCompositingReasons(layer);
     CompositingStateTransitionType compositedLayerUpdate = CompositingLayerAssigner(this).computeCompositedLayerUpdate(layer);
 
     if (compositedLayerUpdate != NoCompositingStateChange)
         setNeedsCompositingUpdate(CompositingUpdateRebuildTree);
 
@@ skipping 744 matching lines @@
     } else if (graphicsLayer == m_scrollLayer.get()) {
         name = "LocalFrame Scrolling Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace WebCore