[SPv2] Implement CSS clip property

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

Index: third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
index bf1341e06917afcfb28654a31892b81382ba8985..b1f001052c6743435f78247f42d1a6d02ec2956e 100644
--- a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
@@ -214,6 +214,45 @@ static PassRefPtr<EffectPaintPropertyNode> createEffectIfNeeded(const LayoutObje
     return newEffectNode.release();
 }
 
+void createCSSClipIfNeeded(RefPtr<ClipPaintPropertyNode>& newClipNodeForCSSClip, RefPtr<ClipPaintPropertyNode>& newClipNodeForCSSClipFixedPosition, const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
+{
+    if (!object.hasClip())
+        return;
+    ASSERT(object.canContainAbsolutePositionObjects());
+
+    // Create clip node for descendants that are not fixed position.
+    // We don't have to setup context.clipForAbsolutePosition here because this object must be
+    // a container for absolute position descendants, and will copy from in-flow context later
+    // at updateOutOfFlowContext() step.
+    LayoutRect clipRect = toLayoutBox(object).clipRect(context.paintOffset);
+    newClipNodeForCSSClip = ClipPaintPropertyNode::create(
+        context.currentTransform,
+        FloatRoundedRect(FloatRect(clipRect)),
+        context.currentClip);
+    context.currentClip = newClipNodeForCSSClip.get();
+
+    // Again, we don't have to setup context.clipForFixedPosition here if this object is
+    // a container for fixed position descendants. It will copy from in-flow context at
+    // updateOutOfFlowContext() step later.
+    // TODO(pdr): Remove the !object.isLayoutView() condition when removing FrameView

[pdr., 2016/03/23 00:53:31]

TODO(trchen)! :)

[trchen, 2016/03/23 01:45:42]

It is copied from updateOutOfFlowContext(). The condition needs to be consistent
so better assign to the same person. I can take over both if you prefer. :)

+    // paint properties for rootLayerScrolls.
+    if (!object.isLayoutView() && object.canContainFixedPositionObjects())
+        return;
+
+    // Now, before creating clip node for fixed position, check whether in-flow context and
+    // fixed-position context has exactly the same clip. Reuse if possible.
+    if (context.currentClip->parent() == context.clipForFixedPosition) {
+        context.clipForFixedPosition = context.currentClip;
+        return;
+    }
+
+    newClipNodeForCSSClipFixedPosition = ClipPaintPropertyNode::create(
+        context.currentTransform,
+        FloatRoundedRect(FloatRect(clipRect)),
+        context.clipForFixedPosition);
+    context.clipForFixedPosition = newClipNodeForCSSClipFixedPosition.get();
+}
+
 // TODO(trchen): Remove this once we bake the paint offset into frameRect.
 static PassRefPtr<TransformPaintPropertyNode> createScrollbarPaintOffsetIfNeeded(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
 {
@@ -354,6 +393,9 @@ void PaintPropertyTreeBuilder::walk(LayoutObject& object, const PaintPropertyTre
     RefPtr<TransformPaintPropertyNode> newTransformNodeForPaintOffsetTranslation = createPaintOffsetTranslationIfNeeded(object, localContext);
     RefPtr<TransformPaintPropertyNode> newTransformNodeForTransform = createTransformIfNeeded(object, localContext);
     RefPtr<EffectPaintPropertyNode> newEffectNode = createEffectIfNeeded(object, localContext);
+    RefPtr<ClipPaintPropertyNode> newClipNodeForCSSClip;
+    RefPtr<ClipPaintPropertyNode> newClipNodeForCSSClipFixedPosition;
+    createCSSClipIfNeeded(newClipNodeForCSSClip, newClipNodeForCSSClipFixedPosition, object, localContext);
     OwnPtr<ObjectPaintProperties::LocalBorderBoxProperties> newRecordedContext = recordTreeContextIfNeeded(object, localContext);
     RefPtr<TransformPaintPropertyNode> newTransformNodeForScrollbarPaintOffset = createScrollbarPaintOffsetIfNeeded(object, localContext);
     RefPtr<ClipPaintPropertyNode> newClipNodeForOverflowClip = createOverflowClipIfNeeded(object, localContext);
@@ -363,11 +405,13 @@ void PaintPropertyTreeBuilder::walk(LayoutObject& object, const PaintPropertyTre
     RefPtr<TransformPaintPropertyNode> newTransformNodeForScrollTranslation = createScrollTranslationIfNeeded(object, localContext);
     updateOutOfFlowContext(object, localContext);
 
-    if (newTransformNodeForPaintOffsetTranslation || newTransformNodeForTransform || newEffectNode || newClipNodeForOverflowClip || newTransformNodeForPerspective || newTransformNodeForScrollTranslation || newTransformNodeForScrollbarPaintOffset || newRecordedContext) {
+    if (newTransformNodeForPaintOffsetTranslation || newTransformNodeForTransform || newEffectNode || newClipNodeForCSSClip || newClipNodeForCSSClipFixedPosition || newClipNodeForOverflowClip || newTransformNodeForPerspective || newTransformNodeForScrollTranslation || newTransformNodeForScrollbarPaintOffset || newRecordedContext) {
         OwnPtr<ObjectPaintProperties> updatedPaintProperties = ObjectPaintProperties::create(
             newTransformNodeForPaintOffsetTranslation.release(),
             newTransformNodeForTransform.release(),
             newEffectNode.release(),
+            newClipNodeForCSSClip.release(),
+            newClipNodeForCSSClipFixedPosition.release(),
             newClipNodeForOverflowClip.release(),
             newTransformNodeForPerspective.release(),
             newTransformNodeForScrollTranslation.release(),