Disable unit tests that fail on cros.

tools/telemetry/telemetry/core/tab_unittest.py

Index: tools/telemetry/telemetry/core/tab_unittest.py
diff --git a/tools/telemetry/telemetry/core/tab_unittest.py b/tools/telemetry/telemetry/core/tab_unittest.py
index 0f2dc7dfc142d53640b67109afaaf53f60df2793..e3b28ffc86287cfd39eeb88bfc4e25afaf1b307b 100644
--- a/tools/telemetry/telemetry/core/tab_unittest.py
+++ b/tools/telemetry/telemetry/core/tab_unittest.py
@@ -6,6 +6,7 @@ import logging
 
 from telemetry.core import util
 from telemetry.core import exceptions
+from telemetry.unittest import DisabledTestOnCrOS
 from telemetry.unittest import tab_test_case
 
 
@@ -55,6 +56,7 @@ class GpuTabTest(tab_test_case.TabTestCase):
     self._extra_browser_args = ['--enable-gpu-benchmarking']
     super(GpuTabTest, self).setUp()
 
+  @DisabledTestOnCrOS
   def testScreenshot(self):
     if not self._tab.screenshot_supported:
       logging.warning('Browser does not support screenshots, skipping test.')
@@ -75,6 +77,7 @@ class GpuTabTest(tab_test_case.TabTestCase):
     screenshot.GetPixelColor(32 * pixel_ratio, 32 * pixel_ratio).AssertIsRGB(
         255, 255, 255, tolerance=2)
 
+  @DisabledTestOnCrOS
   def testScreenshotSync(self):
     if not self._tab.screenshot_supported:
       logging.warning('Browser does not support screenshots, skipping test.')