[SPv2] Adds pre-computed paint property context to PaintLayer.

third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp

 // Copyright 2015 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 "core/paint/PaintPropertyTreeBuilder.h"
 
 #include "core/frame/FrameView.h"
 #include "core/layout/LayoutView.h"
 #include "core/paint/ObjectPaintProperties.h"
 #include "core/paint/PaintLayer.h"
@@ skipping 292 matching lines @@
         context.clipForOutOfFlowPositioned = context.currentClip;
     }
 
     if (createdNewTransform || object.isSVGRoot()) {
         context.transformForFixedPositioned = context.currentTransform;
         context.paintOffsetForFixedPositioned = context.paintOffset;
         context.clipForFixedPositioned = context.currentClip;
     }
 }
 
+PassOwnPtr<ObjectPaintProperties::PropertyTreeContext> cacheTreeContextIfNeeded(LayoutObject& object, const PaintPropertyTreeBuilderContext& context)

[pdr., 2016/02/04 00:06:45]

I still don't really view this as a cache any more than the entire tree is a
cache for efficiently looking up property data.

Rename createAncestorContextIfNeeded? (or similar)?

[trchen, 2016/02/04 00:51:29]

recordTreeContextIfNeeded that is.

+{
+    // Note: Currently only layer painter makes use of the cache. This condition can be changed.
+    if (!object.hasLayer())
+        return nullptr;
+
+    OwnPtr<ObjectPaintProperties::PropertyTreeContext> contextCache = adoptPtr(new ObjectPaintProperties::PropertyTreeContext);
+    contextCache->paintOffset = context.paintOffset;
+    contextCache->properties.transform = context.currentTransform;
+    contextCache->properties.clip = context.currentClip;
+    contextCache->properties.effect = context.currentEffect;
+    return contextCache.release();
+}
+
 void PaintPropertyTreeBuilder::walk(LayoutObject& object, const PaintPropertyTreeBuilderContext& context)
 {
     PaintPropertyTreeBuilderContext localContext(context);
 
     deriveBorderBoxFromContainerContext(object, localContext);
     RefPtr<TransformPaintPropertyNode> newTransformNodeForPaintOffsetTranslation = createPaintOffsetTranslationIfNeeded(object, localContext);
     RefPtr<TransformPaintPropertyNode> newTransformNodeForTransform = createTransformIfNeeded(object, localContext);
     RefPtr<EffectPaintPropertyNode> newEffectNode = createEffectIfNeeded(object, localContext);
+    OwnPtr<ObjectPaintProperties::PropertyTreeContext> newContextCache = cacheTreeContextIfNeeded(object, localContext);
     RefPtr<ClipPaintPropertyNode> newClipNodeForOverflowClip = createOverflowClipIfNeeded(object, localContext);
     // TODO(trchen): Insert flattening transform here, as specified by
     // http://www.w3.org/TR/css3-transforms/#transform-style-property
     RefPtr<TransformPaintPropertyNode> newTransformNodeForPerspective = createPerspectiveIfNeeded(object, localContext);
     RefPtr<TransformPaintPropertyNode> newTransformNodeForScrollTranslation = createScrollTranslationIfNeeded(object, localContext);
     updateOutOfFlowContext(object, newTransformNodeForTransform, localContext);
 
-    if (newTransformNodeForPaintOffsetTranslation || newTransformNodeForTransform || newEffectNode || newClipNodeForOverflowClip || newTransformNodeForPerspective || newTransformNodeForScrollTranslation) {
+    if (newTransformNodeForPaintOffsetTranslation || newTransformNodeForTransform || newEffectNode || newClipNodeForOverflowClip || newTransformNodeForPerspective || newTransformNodeForScrollTranslation || newContextCache) {
         OwnPtr<ObjectPaintProperties> updatedPaintProperties = ObjectPaintProperties::create(
             newTransformNodeForPaintOffsetTranslation.release(),
             newTransformNodeForTransform.release(),
             newEffectNode.release(),
             newClipNodeForOverflowClip.release(),
             newTransformNodeForPerspective.release(),
-            newTransformNodeForScrollTranslation.release());
+            newTransformNodeForScrollTranslation.release(),
+            newContextCache.release());
         object.setObjectPaintProperties(updatedPaintProperties.release());
     } else {
         object.clearObjectPaintProperties();
     }
 
     for (LayoutObject* child = object.slowFirstChild(); child; child = child->nextSibling()) {
         if (child->isBoxModelObject() || child->isSVG())
             walk(*child, localContext);
     }
 }
 
 } // namespace blink