added self time to profiler

lib/liquid/profiler.rb

@@ -44,7 +44,7 @@ module Liquid
     include Enumerable
 
     class Timing
-      attr_reader :code, :partial, :line_number, :children
+      attr_reader :code, :partial, :line_number, :children, :total_time, :self_time
 
       def initialize(node, partial)
         @code        = node.respond_to?(:raw) ? node.raw : node
@@ -63,6 +63,18 @@ module Liquid
 
       def finish
         @end_time = Time.now
+        @total_time = @end_time - @start_time
+        if @children.size == 0
+          @self_time = @total_time
+        else
+          total_children_time = 0
+
+          @children.each do |child|
+            total_children_time += child.total_time
+          end
+
+          @self_time = @total_time - total_children_time
+        end
       end
 
       def render_time