[Telemetry] Enable screenshot taking on Mac

tools/telemetry/telemetry/core/platform_unittest.py

Index: tools/telemetry/telemetry/core/platform_unittest.py
diff --git a/tools/telemetry/telemetry/core/platform_unittest.py b/tools/telemetry/telemetry/core/platform_unittest.py
new file mode 100644
index 0000000000000000000000000000000000000000..8a2983ed50684d9a745814b285750de9688f7aef
--- /dev/null
+++ b/tools/telemetry/telemetry/core/platform_unittest.py
@@ -0,0 +1,37 @@
+# Copyright 2015 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 logging
+import os
+import tempfile
+
+from telemetry import decorators
+from telemetry.util import image_util
+from telemetry.testing import tab_test_case
+
+
+class PlatformScreenshotTest(tab_test_case.TabTestCase):
+  def testScreenshotSupported(self):
+    if self._platform.GetOSName() in ('mac', 'android'):
+      self.assertTrue(self._platform.CanTakeScreenshot())
+
+  # Run this test in serial to avoid multiple browsers pop up on the screen.
+  @decorators.Isolated
+  def testScreenshot(self):
+    if not self._platform.CanTakeScreenshot():
+      logging.warning('Platform does not support screenshots, skipping test.')
+      return
+    tf = tempfile.NamedTemporaryFile(delete=False, suffix='.png')
+    tf.close()
+    try:
+      self.Navigate('screenshot_test.html')
+      self._platform.TakeScreenshot(tf.name)
+      # Assert that screenshot image contains the color of the triangle defined
+      # in screenshot_test.html.
+      img = image_util.FromPngFile(tf.name)
+      screenshot_pixels = image_util.Pixels(img)
+      special_colored_pixel = bytearray([217, 115, 43])
+      self.assertTrue(special_colored_pixel in screenshot_pixels)
+    finally:
+      os.remove(tf.name)