Fix another caret paint invalidation issue

third_party/WebKit/Source/core/editing/CaretDisplayItemClient.cpp

Index: third_party/WebKit/Source/core/editing/CaretDisplayItemClient.cpp
diff --git a/third_party/WebKit/Source/core/editing/CaretDisplayItemClient.cpp b/third_party/WebKit/Source/core/editing/CaretDisplayItemClient.cpp
index 0990fdef8cabca9e3bf7024048e5965ca2a6dc46..acfba08a8a77946c83601c948e92ceb4c38511ea 100644
--- a/third_party/WebKit/Source/core/editing/CaretDisplayItemClient.cpp
+++ b/third_party/WebKit/Source/core/editing/CaretDisplayItemClient.cpp
@@ -125,6 +125,7 @@ void CaretDisplayItemClient::updateStyleAndLayoutIfNeeded(
   // intermediate changes of layoutBlock because they are not painted.
   if (!m_previousLayoutBlock) {
     m_previousLayoutBlock = m_layoutBlock;
+    DCHECK(m_visualRectInPreviousLayoutBlock.isEmpty());
     m_visualRectInPreviousLayoutBlock = m_visualRect;
   }
 
@@ -191,6 +192,7 @@ void CaretDisplayItemClient::invalidatePaintInPreviousLayoutBlock(
   context.paintingLayer->setNeedsRepaint();
   objectInvalidator.invalidateDisplayItemClient(*this, PaintInvalidationCaret);
   m_previousLayoutBlock = nullptr;
+  m_visualRectInPreviousLayoutBlock = LayoutRect();
 }
 
 void CaretDisplayItemClient::invalidatePaintInCurrentLayoutBlock(
@@ -212,8 +214,11 @@ void CaretDisplayItemClient::invalidatePaintInCurrentLayoutBlock(
     }
   }
 
-  if (m_layoutBlock == m_previousLayoutBlock)
+  if (m_layoutBlock == m_previousLayoutBlock &&
+      m_visualRect == m_visualRectInPreviousLayoutBlock) {

[chrishtr, 2017/03/10 05:06:07]

Why is this conditional required? Can't figure this out yet. Add a comment also?

     m_previousLayoutBlock = nullptr;
+    m_visualRectInPreviousLayoutBlock = LayoutRect();
+  }
 
   ObjectPaintInvalidatorWithContext objectInvalidator(*m_layoutBlock, context);
   if (!m_needsPaintInvalidation && newVisualRect == m_visualRect) {