compositor-worker: plumb element id and mutable properties

third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.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
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 45 matching lines @@
 #include "core/paint/TransformRecorder.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/ScriptForbiddenScope.h"
 #include "platform/TraceEvent.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/graphics/paint/CullRect.h"
 #include "platform/graphics/paint/DrawingRecorder.h"
 #include "platform/graphics/paint/PaintController.h"
 #include "platform/graphics/paint/TransformDisplayItem.h"
 #include "public/platform/Platform.h"
+#include "public/platform/WebCompositorMutableProperties.h"
 
 namespace blink {
 
 PaintLayerCompositor::PaintLayerCompositor(LayoutView& layoutView)
     : m_layoutView(layoutView)
     , m_compositingReasonFinder(layoutView)
     , m_pendingUpdateType(CompositingUpdateNone)
     , m_hasAcceleratedCompositing(true)
     , m_compositing(false)
     , m_rootShouldAlwaysCompositeDirty(true)
@@ skipping 308 matching lines @@
                 for (ScrollableArea* scrollableArea : *scrollableAreas)
                     layersChanged |= scrollableArea->updateAfterCompositingChange();
             }
         }
 
         if (layersChanged)
             updateType = std::max(updateType, CompositingUpdateRebuildTree);
     }
 
     if (updateType != CompositingUpdateNone) {
+        // FIXME: it should not be necessary to check that the document has no child needing a style recalc. See crbug.com/552847
+        if (RuntimeEnabledFeatures::compositorWorkerEnabled() && m_scrollLayer && !m_layoutView.document().childNeedsStyleRecalc()) {

[chrishtr, 2015/11/24 16:22:50]

What is actually happening? Let's squash this bug now.

[Ian Vollick, 2015/11/25 18:28:45]

This is an old, unrelated video bug
(https://code.google.com/p/chromium/issues/detail?id=372245).
LayoutTextTrackContainerElement changes style information during layout. The
consequence is that when we ask for the scrollingElement after layout, it
sometimes complains in debug mode due to an assertion about dirty style. IIUC,
fixing this properly involves getting a w3c spec change made related to video
height/width.

I've changed my approach in the latest patch set. Rather than putting the
workaround in shipping code here, I've exposed the compositor worker feature via
InternalSettings so that I can disable it only for the two video layout tests
that invoke this style-update-during-layout behavior, tests that are closely
related to the linked bug.

+            if (Element* scrollingElement = m_layoutView.document().scrollingElement()) {
+                uint64_t elementId = 0;
+                uint32_t mutableProperties = WebCompositorMutablePropertyNone;
+                if (scrollingElement->hasCompositorProxy()) {
+                    elementId = DOMNodeIds::idForNode(scrollingElement);
+                    mutableProperties = WebCompositorMutablePropertyScrollLeft | WebCompositorMutablePropertyScrollTop;
+                }
+                m_scrollLayer->setElementId(elementId);
+                m_scrollLayer->setMutableProperties(mutableProperties);
+            }
+        }
+
         GraphicsLayerUpdater updater;
         updater.update(*updateRoot, layersNeedingPaintInvalidation);
 
         if (updater.needsRebuildTree())
             updateType = std::max(updateType, CompositingUpdateRebuildTree);
 
 #if ENABLE(ASSERT)
         // FIXME: Move this check to the end of the compositing update.
         GraphicsLayerUpdater::assertNeedsToUpdateGraphicsLayerBitsCleared(*updateRoot);
 #endif
@@ skipping 800 matching lines @@
     } else if (graphicsLayer == m_scrollLayer.get()) {
         name = "Frame Scrolling Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace blink