Replace the existing SpdyHeaderBlock typedef with a class.

net/spdy/spdy_session.cc

Index: net/spdy/spdy_session.cc
diff --git a/net/spdy/spdy_session.cc b/net/spdy/spdy_session.cc
index f5ae506ad37fec46bb672e6d6da534f3e0ec579d..4055422f3137b1fa5baa74a0d45f3da89c817cc9 100644
--- a/net/spdy/spdy_session.cc
+++ b/net/spdy/spdy_session.cc
@@ -66,8 +66,9 @@ scoped_ptr<base::ListValue> SpdyHeaderBlockToListValue(
   for (SpdyHeaderBlock::const_iterator it = headers.begin();
        it != headers.end(); ++it) {
     headers_list->AppendString(
-        it->first + ": " +
-        ElideHeaderValueForNetLog(capture_mode, it->first, it->second));
+        it->first.as_string() + ": " +
+        ElideHeaderValueForNetLog(capture_mode, it->first.as_string(),
+                                  it->second.as_string()));
   }
   return headers_list.Pass();
 }