Add CaretBase::m_caretPainter, and compute caretBrowsing lazily.

Source/core/editing/Caret.cpp

Index: Source/core/editing/Caret.cpp
diff --git a/Source/core/editing/Caret.cpp b/Source/core/editing/Caret.cpp
index 52116d87df1002be37eca30e9f358d1a946f5985..4afb89d11851d0758e1b1e131f8e78f635382aef 100644
--- a/Source/core/editing/Caret.cpp
+++ b/Source/core/editing/Caret.cpp
@@ -40,7 +40,8 @@
 namespace blink {
 
 CaretBase::CaretBase(CaretVisibility visibility)
-    : m_caretVisibility(visibility)
+    : m_caretPainter(nullptr)
+    , m_caretVisibility(visibility)
 {
 }
 
@@ -115,6 +116,7 @@ DEFINE_TRACE(DragCaretController)
 
 void CaretBase::clearCaretRect()
 {
+    m_caretPainter = nullptr;
     m_caretLocalRect = LayoutRect();
 }
 
@@ -162,6 +164,7 @@ static void mapCaretRectToCaretPainter(LayoutObject* caretLayoutObject, LayoutBl
 
 bool CaretBase::updateCaretRect(Document* document, const PositionWithAffinity& caretPosition)
 {
+    m_caretPainter = nullptr;
     m_caretLocalRect = LayoutRect();
 
     if (caretPosition.position().isNull())
@@ -175,9 +178,9 @@ bool CaretBase::updateCaretRect(Document* document, const PositionWithAffinity&
 
     // Get the layoutObject that will be responsible for painting the caret
     // (which is either the layoutObject we just found, or one of its containers).
-    LayoutBlock* caretPainter = caretLayoutObject(caretPosition.position().deprecatedNode());
+    m_caretPainter = caretLayoutObject(caretPosition.position().deprecatedNode());
 
-    mapCaretRectToCaretPainter(layoutObject, caretPainter, m_caretLocalRect);
+    mapCaretRectToCaretPainter(layoutObject, m_caretPainter, m_caretLocalRect);
 
     return true;
 }
@@ -187,11 +190,6 @@ bool CaretBase::updateCaretRect(Document* document, const VisiblePosition& caret
     return updateCaretRect(document, PositionWithAffinity(caretPosition.deepEquivalent(), caretPosition.affinity()));
 }
 
-LayoutBlock* DragCaretController::caretLayoutObject() const
-{
-    return CaretBase::caretLayoutObject(m_position.deepEquivalent().deprecatedNode());
-}
-
 IntRect CaretBase::absoluteBoundsForLocalRect(Node* node, const LayoutRect& rect) const
 {
     LayoutBlock* caretPainter = caretLayoutObject(node);