Invalidate the previous caret even if the parent text node is removed.

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

Index: third_party/WebKit/Source/core/editing/FrameSelection.cpp
diff --git a/third_party/WebKit/Source/core/editing/FrameSelection.cpp b/third_party/WebKit/Source/core/editing/FrameSelection.cpp
index b51173b7bff61bb2ec2393b037a0360637a3abdf..d88af3460da90d27f4777cf8b147f16a956a6a6e 100644
--- a/third_party/WebKit/Source/core/editing/FrameSelection.cpp
+++ b/third_party/WebKit/Source/core/editing/FrameSelection.cpp
@@ -95,6 +95,7 @@ FrameSelection::FrameSelection(LocalFrame* frame)
     , m_pendingSelection(PendingSelection::create(*this))
     , m_selectionEditor(SelectionEditor::create(*this))
     , m_granularity(CharacterGranularity)
+    , m_parentOfPreviousCaretNode(nullptr)
     , m_previousCaretVisibility(Hidden)
     , m_caretBlinkTimer(this, &FrameSelection::caretBlinkTimerFired)
     , m_caretRectDirty(true)
@@ -634,6 +635,7 @@ void FrameSelection::prepareForDestruction()
     setSelection(VisibleSelection(), CloseTyping | ClearTypingStyle | DoNotUpdateAppearance);
     m_selectionEditor->dispose();
     m_previousCaretNode.clear();
+    m_parentOfPreviousCaretNode = nullptr;
 }
 
 void FrameSelection::setStart(const VisiblePosition &pos, EUserTriggered trigger)
@@ -717,7 +719,12 @@ void FrameSelection::invalidateCaretRect()
         invalidateLocalCaretRect(m_previousCaretNode.get(), m_previousCaretRect);
     if (newNode && (shouldRepaintCaret(*newNode) || shouldRepaintCaret(view)))
         invalidateLocalCaretRect(newNode, newRect);
+    // Must invalidate #text even if it's detached. crbug.com/528922
+    if (m_previousCaretNode && newNode == m_parentOfPreviousCaretNode && !m_previousCaretNode->inDocument())

[yosin_UTC9, 2016/02/05 04:04:48]

This condition isn't enough, e.g. 
 - ancestor of |m_previousCaretNode| can be detached from document.
 - |m_previousCaretNode| can be move into another tree location.

I don't think this approach is good.

+        invalidateLocalCaretRect(newNode, m_previousCaretRect);
     m_previousCaretNode = newNode;
+    if (newNode)
+        m_parentOfPreviousCaretNode = newNode->parentNode();
     m_previousCaretRect = newRect;
     m_previousCaretVisibility = caretVisibility();
 }