[Telemetry] Clean separation between tab (public) and tab_backend (Chrome); second attempt.

tools/telemetry/telemetry/tab_unittest.py

Index: tools/telemetry/telemetry/tab_unittest.py
diff --git a/tools/telemetry/telemetry/tab_unittest.py b/tools/telemetry/telemetry/tab_unittest.py
index f6906b27e4a8c2bedbeafc27a59fcf19a0f2b2e0..67ae6690d671836f9e2ba6f4fff963aa82dd2c5d 100644
--- a/tools/telemetry/telemetry/tab_unittest.py
+++ b/tools/telemetry/telemetry/tab_unittest.py
@@ -1,6 +1,8 @@
 # Copyright (c) 2012 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 import tab_test_case
 from telemetry import tab_crash_exception
 from telemetry import util
@@ -8,6 +10,7 @@ from telemetry import util
 
 def _IsDocumentVisible(tab):
   state = tab.runtime.Evaluate('document.webkitVisibilityState')
+  # TODO(dtu): Remove when crbug.com/166243 is fixed.
   tab.Disconnect()
   return state == 'visible'
 
@@ -40,3 +43,24 @@ class TabTest(tab_test_case.TabTestCase):
     util.WaitFor(lambda: _IsDocumentVisible(self._tab), timeout=5)
     self.assertFalse(_IsDocumentVisible(new_tab))
 
+
+class GpuTabTest(tab_test_case.TabTestCase):
+  def setUp(self):
+    self._extra_browser_args = ['--enable-gpu-benchmarking']
+    super(GpuTabTest, self).setUp()
+
+  def testScreenshot(self):
+    unittest_data_dir = os.path.join(os.path.dirname(__file__),
+                                     '..', 'unittest_data')
+    self._browser.SetHTTPServerDirectory(unittest_data_dir)
+    self._tab.page.Navigate(
+      self._browser.http_server.UrlOf('green_rect.html'))
+    self._tab.WaitForDocumentReadyStateToBeComplete()
+
+    # Skip this test if running against a browser without screenshot support
+    if self._tab.screenshot_supported:
+      screenshot = self._tab.Screenshot(5)
+      assert screenshot
+      screenshot.GetPixelColor(0, 0).AssertIsRGB(0, 255, 0)
+      screenshot.GetPixelColor(31, 31).AssertIsRGB(0, 255, 0)
+      screenshot.GetPixelColor(32, 32).AssertIsRGB(255, 255, 255)