[Telemetry] Add tab property "dom_stats".

Currently, the associated function reaches into the inspector_backend, which in
turn now has a new module to communicate with the remote inspector's
"Memory" domain.  This allows us to query the remote inspector for the
DOM node count, document count, and event listener count, for a tab.

Making this change is a prerequisite to converting the Chrome Endure
endurance tests over to Telemetry from their current pyauto-based
implementation.

BUG=chromium-os:39589
TEST=tools/telemetry/run_tests InspectorMemoryTest

Review URL: https://chromiumcodereview.appspot.com/12800004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@188092 0039d316-1c4b-4281-b951-d872f2087c98

5 files changed, 114 insertions, 0 deletions

diff --git a/tools/telemetry/telemetry/core/chrome/inspector_backend.py b/tools/telemetry/telemetry/core/chrome/inspector_backend.py
index 8a5f8b1..ee5c06c 100644
--- a/tools/telemetry/telemetry/core/chrome/inspector_backend.py
+++ b/tools/telemetry/telemetry/core/chrome/inspector_backend.py
@@ -9,6 +9,7 @@ import sys
 from telemetry.core import util
 from telemetry.core import exceptions
 from telemetry.core.chrome import inspector_console
+from telemetry.core.chrome import inspector_memory
 from telemetry.core.chrome import inspector_page
 from telemetry.core.chrome import inspector_runtime
 from telemetry.core.chrome import inspector_timeline
@@ -30,6 +31,7 @@ class InspectorBackend(object):
     self._next_request_id = 0
 
     self._console = inspector_console.InspectorConsole(self)
+    self._memory = inspector_memory.InspectorMemory(self)
     self._page = inspector_page.InspectorPage(self)
     self._runtime = inspector_runtime.InspectorRuntime(self)
     self._timeline = inspector_timeline.InspectorTimeline(self)
@@ -152,6 +154,16 @@ class InspectorBackend(object):
   def message_output_stream(self, stream):  # pylint: disable=E0202
     self._console.message_output_stream = stream
 
+  # Memory public methods.
+
+  def GetDOMStats(self, timeout):
+    dom_counters = self._memory.GetDOMCounters(timeout)
+    return {
+      'document_count': dom_counters['documents'],
+      'node_count': dom_counters['nodes'],
+      'event_listener_count': dom_counters['jsEventListeners']
+    }
+
   # Page public methods.
 
   def PerformActionAndWaitForNavigate(self, action_function, timeout):
diff --git a/tools/telemetry/telemetry/core/chrome/inspector_memory.py b/tools/telemetry/telemetry/core/chrome/inspector_memory.py
new file mode 100644
index 0000000..931cb6e
--- /dev/null
+++ b/tools/telemetry/telemetry/core/chrome/inspector_memory.py
@@ -0,0 +1,50 @@
+# Copyright (c) 2013 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+import json
+
+class InspectorMemoryException(Exception):
+  pass
+
+class InspectorMemory(object):
+  """Communicates with the remote inspector's Memory domain."""
+
+  def __init__(self, inspector_backend):
+    self._inspector_backend = inspector_backend
+    self._inspector_backend.RegisterDomain(
+        'Memory',
+        self._OnNotification,
+        self._OnClose)
+
+  def _OnNotification(self, msg):
+    pass
+
+  def _OnClose(self):
+    pass
+
+  def GetDOMCounters(self, timeout):
+    """Retrieves DOM element counts.
+
+    Args:
+      timeout: The number of seconds to wait for the inspector backend to
+          service the request before timing out.
+
+    Returns:
+      A dictionary containing the counts associated with "nodes", "documents",
+      and "jsEventListeners".
+    """
+    res = self._inspector_backend.SyncRequest({
+      'method': 'Memory.getDOMCounters'
+    }, timeout)
+    if ('result' not in res or
+        'nodes' not in res['result'] or
+        'documents' not in res['result'] or
+        'jsEventListeners' not in res['result']):
+      raise InspectorMemoryException(
+          'Inspector returned unexpected result for Memory.getDOMCounters:\n' +
+          json.dumps(res, indent=2))
+    return {
+        'nodes': res['result']['nodes'],
+        'documents': res['result']['documents'],
+        'jsEventListeners': res['result']['jsEventListeners']
+    }
diff --git a/tools/telemetry/telemetry/core/chrome/inspector_memory_unittest.py b/tools/telemetry/telemetry/core/chrome/inspector_memory_unittest.py
new file mode 100644
index 0000000..a84be78
--- /dev/null
+++ b/tools/telemetry/telemetry/core/chrome/inspector_memory_unittest.py
@@ -0,0 +1,21 @@
+# Copyright (c) 2013 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+import os
+
+from telemetry.test import tab_test_case
+
+class InspectorMemoryTest(tab_test_case.TabTestCase):
+  def testGetDOMStats(self):
+    unittest_data_dir = os.path.join(os.path.dirname(__file__),
+                                     '..', '..', '..', 'unittest_data')
+    self._browser.SetHTTPServerDirectory(unittest_data_dir)
+
+    self._tab.Navigate(
+      self._browser.http_server.UrlOf('dom_counter_sample.html'))
+    self._tab.WaitForDocumentReadyStateToBeComplete()
+
+    counts = self._tab.dom_stats
+    self.assertEqual(counts['document_count'], 1)
+    self.assertEqual(counts['node_count'], 14)
+    self.assertEqual(counts['event_listener_count'], 2)
diff --git a/tools/telemetry/telemetry/core/tab.py b/tools/telemetry/telemetry/core/tab.py
index 6e5c804..979b645 100644
--- a/tools/telemetry/telemetry/core/tab.py
+++ b/tools/telemetry/telemetry/core/tab.py
@@ -31,6 +31,25 @@ class Tab(web_contents.WebContents):
   def url(self):
     return self._inspector_backend.url
 
+  @property
+  def dom_stats(self):
+    """A dictionary populated with measured DOM statistics.
+
+    Currently this dictionary contains:
+    {
+      'document_count': integer,
+      'node_count': integer,
+      'event_listener_count': integer
+    }
+    """
+    dom_counters = self._inspector_backend.GetDOMStats(
+        timeout=DEFAULT_TAB_TIMEOUT)
+    assert (len(dom_counters) == 3 and
+            all([x in dom_counters for x in ['document_count', 'node_count',
+                                             'event_listener_count']]))
+    return dom_counters
+
+
   def Activate(self):
     """Brings this tab to the foreground asynchronously.
 
diff --git a/tools/telemetry/unittest_data/dom_counter_sample.html b/tools/telemetry/unittest_data/dom_counter_sample.html
new file mode 100644
index 0000000..483d1e0
--- /dev/null
+++ b/tools/telemetry/unittest_data/dom_counter_sample.html
@@ -0,0 +1,12 @@
+<html>
+  <title>DOM counter unit test page</title>
+  <body>
+    <h1 onclick="">Webpage to be used for DOM counter unit testing.</h1>
+    <p onclick="">
+      This webpage is meant to be used by a unit test that checks DOM element
+      counters.  The test expects there to be exactly 1 document, 14 nodes,
+      and 2 event listeners.  Beware, modifying the HTML of this page may
+      change the element count, causing the unit test to fail!
+    </p>
+  </body>
+</html>