(WIP) Invalidation during painting (for synchronized painting)

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

Index: third_party/WebKit/Source/core/paint/LineBoxListPainter.cpp
diff --git a/third_party/WebKit/Source/core/paint/LineBoxListPainter.cpp b/third_party/WebKit/Source/core/paint/LineBoxListPainter.cpp
index 9415606348ee67c0743bf2b277a57f8065b220b3..8b61ab28ffecb579041b0c1b1c7df824b4a19df7 100644
--- a/third_party/WebKit/Source/core/paint/LineBoxListPainter.cpp
+++ b/third_party/WebKit/Source/core/paint/LineBoxListPainter.cpp
@@ -60,24 +60,34 @@ void LineBoxListPainter::paint(const LayoutBoxModelObject& layoutObject, const P
     }
 }
 
-static void invalidateLineBoxPaintOffsetsInternal(PaintController& paintController, InlineFlowBox* inlineBox)
+static void invalidateLineBoxPaintOffsetsInternal(const LayoutObject& layoutObject, PaintController& paintController, InlineFlowBox* inlineBox)
 {
-    paintController.invalidatePaintOffset(*inlineBox);
+    ASSERT(layoutObject == inlineBox->layoutObject());
+
+    if (!inlineBox->isRootInlineBox())
+        paintController.invalidatePaintOffset(*inlineBox);
+
     for (InlineBox* child = inlineBox->firstChild(); child; child = child->nextOnLine()) {
+        if (layoutObject != child->layoutObject())
+            continue;
         if (!child->lineLayoutItem().isText() && child->boxModelObject().hasSelfPaintingLayer())
             continue;
         if (child->isInlineFlowBox())
-            invalidateLineBoxPaintOffsetsInternal(paintController, toInlineFlowBox(child));
+            invalidateLineBoxPaintOffsetsInternal(layoutObject, paintController, toInlineFlowBox(child));
         else
             paintController.invalidatePaintOffset(*child);
     }
 }
 
-void LineBoxListPainter::invalidateLineBoxPaintOffsets(const PaintInfo& paintInfo) const
+void LineBoxListPainter::invalidateLineBoxPaintOffsets(const LayoutObject& layoutObject, const PaintInfo& paintInfo) const
 {
     PaintController& paintController = paintInfo.context.paintController();
-    for (InlineFlowBox* curr = m_lineBoxList.firstLineBox(); curr; curr = curr->nextLineBox())
-        invalidateLineBoxPaintOffsetsInternal(paintController, curr);
+    for (InlineFlowBox* curr = m_lineBoxList.firstLineBox(); curr; curr = curr->nextLineBox()) {
+        // Invalidate paint offsets of the line boxes directly contained by the layoutObject.
+        // The other line boxes will be handled by their direct container layout objects.
+        if (layoutObject == curr->layoutObject())
+            invalidateLineBoxPaintOffsetsInternal(layoutObject, paintController, curr);
+    }
 }
 
 } // namespace blink