Disable drawing recorder cache for carets

Source/core/paint/BlockPainter.cpp

Index: Source/core/paint/BlockPainter.cpp
diff --git a/Source/core/paint/BlockPainter.cpp b/Source/core/paint/BlockPainter.cpp
index 809f8ba106cf29a26706314efc9060c4a52080ff..cbc61e389864e0a63d8a7123eaf52b15f54ebb9a 100644
--- a/Source/core/paint/BlockPainter.cpp
+++ b/Source/core/paint/BlockPainter.cpp
@@ -225,7 +225,7 @@ void BlockPainter::paintObject(const PaintInfo& paintInfo, const LayoutPoint& pa
     // If the caret's node's render object's containing block is this block, and the paint action is PaintPhaseForeground,
     // then paint the caret.
     if (paintPhase == PaintPhaseForeground) {
-        RenderDrawingRecorder recorder(paintInfo.context, &m_renderBlock, paintPhase, bounds);
+        RenderDrawingRecorder recorder(paintInfo.context, &m_renderBlock, paintPhase, bounds, DrawingRecorder::DisableCache);

[chrishtr, 2014/12/12 00:18:01]

Add a comment explaining the situation. Also, how exactly do carets paint
without invalidation?

How much work is it for carets to start invalidating their containing block?

[Xianzhu, 2014/12/12 00:24:16]

Actually we already invalidated carets within their containing block. We just
miss the invalidation when caretBrowsing setting changes which is a common bug
of all paint modes. I'm looking into the bug.

This shows that our cached display item assertions are good to discover
under-invalidation bugs :)

         paintCarets(paintInfo, paintOffset);
     }
 }