Bug 504311. Don't reframe text when white-space changes between preformatted values, or between non-preformatted values. r=bz

--HG--
extra : rebase_source : 7f545ad1d85bcda74d18d9308539b45149a4a194

layout/style/crashtests/504311-1.xul

@@ -0,0 +1,24 @@
+<?xml version="1.0"?>
+<?xml-stylesheet href="chrome://global/skin" type="text/css"?>
+
+<window xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
+        onload="f()">
+
+	<script type="text/javascript">
+		<![CDATA[
+			function f ()
+			{
+                netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
+                var tb = document. getElementById ("tb01");
+				var inputField = tb. inputField;
+				var editor = inputField. QueryInterface (Components. interfaces. nsIDOMNSEditableElement). editor;
+				editor = editor. QueryInterface (Components. interfaces. nsIEditor);
+				editor = editor. QueryInterface (Components. interfaces. nsIPlaintextEditor);
+				editor. wrapWidth = -1;
+			}
+		]]>
+	</script>
+	
+	<textbox id="tb01" multiline="true"/>
+
+</window>

layout/style/crashtests/crashtests.list

@@ -39,3 +39,4 @@ load 473914-1.html
 skip load long-url-list-stack-overflow.html # skipped due to being slow (bug 477490)
 load 495269-1.html
 load 495269-2.html
+load 504311-1.xul

layout/style/nsStyleStruct.cpp

@@ -1873,13 +1873,14 @@ nsStyleText::~nsStyleText(void) { }
 
 nsChangeHint nsStyleText::CalcDifference(const nsStyleText& aOther) const
 {
-  if (mWhiteSpace != aOther.mWhiteSpace) {
+  if (NewlineIsSignificant() != aOther.NewlineIsSignificant()) {
     // This may require construction of suppressed text frames
     return NS_STYLE_HINT_FRAMECHANGE;
   }
 
   if ((mTextAlign != aOther.mTextAlign) ||
       (mTextTransform != aOther.mTextTransform) ||
+      (mWhiteSpace != aOther.mWhiteSpace) ||
       (mWordWrap != aOther.mWordWrap) ||
       (mLetterSpacing != aOther.mLetterSpacing) ||
       (mLineHeight != aOther.mLineHeight) ||