StylePropertySerializer should expand all property if needed.

LayoutTests/editing/style/push-down-inline-styles-expected.txt

Index: LayoutTests/editing/style/push-down-inline-styles-expected.txt
diff --git a/LayoutTests/editing/style/push-down-inline-styles-expected.txt b/LayoutTests/editing/style/push-down-inline-styles-expected.txt
index 030d6f5358883d996696ea92341366d3c932adbc..f81fe07f71ff3ed430fc85777112348247e28eee 100644
--- a/LayoutTests/editing/style/push-down-inline-styles-expected.txt
+++ b/LayoutTests/editing/style/push-down-inline-styles-expected.txt
@@ -20,8 +20,8 @@ PASS underline converted <span style="text-decoration: underline;"><div id="test
 PASS underline converted <span style="text-decoration: underline;"><div id="test">hello</div><blockquote>world<br>webkit</blockquote></span> to <div id="test">hello</div><blockquote style="text-decoration-line: underline;">world<br>webkit</blockquote>
 PASS underline converted <span style="text-decoration: underline;">hello<div id="test">world</div>webkit</u> to <u>hello</u><div id="test">world</div><u>webkit</u>
 FAIL underline converted <div style="text-decoration: underline;"><div>hello</span></div><div id="test">webkit</div><span style="font-style: italic;">rocks</span> to <div><div style="text-decoration-line: underline;">hello</div><div id="test">webkit</div><span style="text-decoration-line: underline; font-style: italic;">rocks</span></div>, expected <div><div style="text-decoration-line: underline;">hello</span></div><div id="test">webkit</div><u><span style="font-style: italic;">rocks</span></u></div>
-PASS underline converted <span style="text-decoration: underline;"><div style="text-decoration: line-through;">hello</div><div id="test">world</div></span> to <div style="text-decoration-line: underline line-through;">hello</div><div id="test">world</div>
-PASS strikeThrough converted <span style="text-decoration: line-through;"><div id="test">hello</div><div style="text-decoration: underline;">world</div></span> to <div id="test">hello</div><div style="text-decoration-line: line-through underline;">world</div>
+PASS underline converted <span style="text-decoration-line: underline;"><div style="text-decoration-line: line-through;">hello</div><div id="test">world</div></span> to <div style="text-decoration-line: underline line-through;">hello</div><div id="test">world</div>
+PASS strikeThrough converted <span style="text-decoration-line: line-through;"><div id="test">hello</div><div style="text-decoration-line: underline;">world</div></span> to <div id="test">hello</div><div style="text-decoration-line: line-through underline;">world</div>
 PASS successfullyParsed is true
 
 TEST COMPLETE