Adding a test for measuring memory usage.

tools/perf/page_sets/top_25_usage.json

Index: tools/perf/page_sets/top_25_usage.json
diff --git a/tools/perf/page_sets/top_25_usage.json b/tools/perf/page_sets/top_25_usage.json
new file mode 100644
index 0000000000000000000000000000000000000000..6c0088a2438319bb42544eba64ea132ed0270751
--- /dev/null
+++ b/tools/perf/page_sets/top_25_usage.json
@@ -0,0 +1,31 @@
+{
+    "description": "Pages for executing tests which not only load the pages, but also do some user actions.",
+    "credentials_path": "../data/credentials.json",
+    "archive_path": "../data/top_25_usage.wpr",
+    "pages": [
+        {
+            "name": "Facebook",
+            "url": "http://www.facebook.com/barackobama",
+            "why": "top social,Public profile",
+            "credentials": "facebook",
+            "scroll_is_infinite": true,
+            "interactions": [
+                {
+                    "type": "TestHelper",
+                    "code": "window.__ClickLinkWithText(\"Women for Obama\");",
+		    "completion": "window.__ReadyStateComplete()"
+                },
+                {
+                    "type": "TestHelper",
+                    "code": "window.__ClickLinkWithText(\"About\");",
+		    "completion": "window.__ReadyStateComplete()"
+                },
+                {
+                    "type": "TestHelper",
+                    "code": "window.__ClickLinkWithText(\"Home\");",
+		    "completion": "window.__ReadyStateComplete()"
+                }
+            ]
+        }
+    ]
+}