DevTools: use timing information for "disk cached" resources.

LayoutTests/http/tests/inspector/network/resources/cached-script.php

Index: LayoutTests/http/tests/inspector/network/resources/cached-script.php
diff --git a/LayoutTests/http/tests/inspector/network/resources/cached-script.php b/LayoutTests/http/tests/inspector/network/resources/cached-script.php
new file mode 100644
index 0000000000000000000000000000000000000000..9f064b7b40706a895bdc99d2ce1418b7f3e4221b
--- /dev/null
+++ b/LayoutTests/http/tests/inspector/network/resources/cached-script.php
@@ -0,0 +1,12 @@
+<?php
+    if ($_SERVER["HTTP_IF_MODIFIED_SINCE"]) {
+        header("HTTP/1.0 304 Not Modified");
+        exit;
+    }
+
+    header("Cache-control: max-age=3600");
+    header("Expires: " . gmdate(DATE_RFC1123, time() + 600));
+    header("Last-Modified: " . gmdate(DATE_RFC1123, time() - 600));
+    header("Content-Type:text/javascript; charset=UTF-8");
+?>
+console.log("Done.");