libsysprof-analyze: make mark catalog work with sections

This allows us more flexibility with creating sections usin the flatten
list model as the rows need to contain the data for the headers.

src/libsysprof-gtk/style.css

@@ -66,3 +66,7 @@ callgraphview row:not(:selected) treeexpander symbol.unwindable {
 marktable {
   font-size: .9em;
 }
+
+markchart {
+  font-size: .9em;
+}