Traverse into child LayoutViews during invalidateTreeIfNeeded

Source/core/layout/LayoutPart.cpp

Index: Source/core/layout/LayoutPart.cpp
diff --git a/Source/core/layout/LayoutPart.cpp b/Source/core/layout/LayoutPart.cpp
index cae3fb991c9aa9970659e306f186f9fd9452063c..386307ba04359916b69506cfdcdcc2af01c29a29 100644
--- a/Source/core/layout/LayoutPart.cpp
+++ b/Source/core/layout/LayoutPart.cpp
@@ -331,4 +331,17 @@ bool LayoutPart::setWidgetGeometry(const LayoutRect& frame)
     return widget->frameRect().size() != newFrame.size();
 }
 
+PaintInvalidationReason LayoutPart::invalidatePaintIfNeeded(PaintInvalidationState& paintInvalidationState, const LayoutBoxModelObject& paintInvalidationContainer)
+{
+    if (widget() && widget()->isFrameView()) {
+        LayoutView* childLayoutView = toFrameView(widget())->layoutView();
+        if (!childLayoutView->isPaintInvalidationContainer()) {

[chrishtr, 2015/06/26 23:32:46]

Why can't you just pass down these parameters in the PaintInvalidationState
itself?

[Xianzhu, 2015/06/27 00:17:15]

We don't walk into the sub frames during a paint invalidation of a frame. The
FrameView recursively call LayoutView::invalidateTreeIfNeeded() for each frame
each with a new PaintInvalidationState. This CL let the new
PaintInvalidationStates get the states saved during the parent frame's
invalidateTreeIfNeeded().

Another way might be to let LayoutView::invalidateTreeIfNeeded() walk into sub
frames, and mark ancestor paint invalidation flags across frame boundaries. I'm
not sure how risky it is to do this.

[chrishtr, 2015/06/29 17:42:28]

This does seem a cleaner approach. To make it easier/safer, maybe just
FrameView::invalidateTreeIfNeeded() into LayoutView so you can call it from
here?

+            childLayoutView->setForceCheckForPaintInvalidationByParent(paintInvalidationState.forceCheckForPaintInvalidation());
+            childLayoutView->setPaintInvalidationCachedOffsetsEnabledByParent(paintInvalidationState.cachedOffsetsEnabled());
+        }
+    }
+
+    return LayoutReplaced::invalidatePaintIfNeeded(paintInvalidationState, paintInvalidationContainer);
+}
+
 }