Use more const references in MarkupAccumulator and its subclasses

Source/core/editing/HTMLInterchange.cpp

Index: Source/core/editing/HTMLInterchange.cpp
diff --git a/Source/core/editing/HTMLInterchange.cpp b/Source/core/editing/HTMLInterchange.cpp
index c63d98c66c93261e6decd8b8cda37fd045e551d1..403ca007caa580a97b61043e41e8f31e22d79898 100644
--- a/Source/core/editing/HTMLInterchange.cpp
+++ b/Source/core/editing/HTMLInterchange.cpp
@@ -34,10 +34,10 @@
 
 namespace WebCore {
 
-String convertHTMLTextToInterchangeFormat(const String& in, const Text* node)
+String convertHTMLTextToInterchangeFormat(const String& in, const Text& node)
 {
     // Assume all the text comes from node.
-    if (node->renderer() && node->renderer()->style()->preserveNewline())
+    if (node.renderer() && node.renderer()->style()->preserveNewline())
         return in;
 
     const char convertedSpaceString[] = "<span class=\"" AppleConvertedSpace "\">\xA0</span>";