Fix race conditions in window snapshot code.

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 f555dc2812745a06c927cc1517a102b31bfcc07b..469015abb6f7bfae3d1cb96dd50df2728837441b 100644
--- a/tools/telemetry/telemetry/core/tab_unittest.py
+++ b/tools/telemetry/telemetry/core/tab_unittest.py
@@ -3,12 +3,10 @@
 # found in the LICENSE file.
 
 import logging
-import time
 
 from telemetry.core import util
 from telemetry.core import exceptions
 from telemetry.unittest import tab_test_case
-from telemetry.unittest import DisabledTest
 
 
 def _IsDocumentVisible(tab):
@@ -56,7 +54,6 @@ class GpuTabTest(tab_test_case.TabTestCase):
     self._extra_browser_args = ['--enable-gpu-benchmarking']
     super(GpuTabTest, self).setUp()
 
-  @DisabledTest
   def testScreenshot(self):
     if not self._tab.screenshot_supported:
       logging.warning('Browser does not support screenshots, skipping test.')
@@ -68,8 +65,6 @@ class GpuTabTest(tab_test_case.TabTestCase):
     self._tab.WaitForDocumentReadyStateToBeComplete()
     pixel_ratio = self._tab.EvaluateJavaScript('window.devicePixelRatio || 1')
 
-    # TODO(bajones): Sleep for a bit to counter BUG 260878.
-    time.sleep(0.5)
     screenshot = self._tab.Screenshot(5)
     assert screenshot
     screenshot.GetPixelColor(0 * pixel_ratio, 0 * pixel_ratio).AssertIsRGB(
@@ -78,3 +73,19 @@ class GpuTabTest(tab_test_case.TabTestCase):
         0, 255, 0, tolerance=2)
     screenshot.GetPixelColor(32 * pixel_ratio, 32 * pixel_ratio).AssertIsRGB(
         255, 255, 255, tolerance=2)
+
+  def testScreenshotSync(self):

[bajones, 2013/09/27 20:50:11]

Screenshot sync test has been added to telemetry's unittests. I was going to add
it to content/test/gpu_tests but then it's a separate telemetry test type that
will need to be added to the recipes. This felt more natural in the end. (cc/
kbr@)

[Ken Russell (switch to Gerrit), 2013/09/27 22:42:39]

In order to provide complete coverage, the test will have to be run (for the
time being) with both the legacy software path and the compositor. It's fine in
my opinion to have it as part of telemetry's unit tests, but this will only be
testing one of these two configurations. Eventually we should invoke it as part
of the GPU bots' tests in both configurations.

+    if not self._tab.screenshot_supported:
+      logging.warning('Browser does not support screenshots, skipping test.')
+      return
+
+    self._browser.SetHTTPServerDirectories(util.GetUnittestDataDir())
+    self._tab.Navigate(
+      self._browser.http_server.UrlOf('screenshot_sync.html'))
+    self._tab.WaitForDocumentReadyStateToBeComplete()
+
+    def IsTestComplete():
+      return self._tab.EvaluateJavaScript('window.__testComplete')
+    util.WaitFor(IsTestComplete, 120)
+
+    assert self._tab.EvaluateJavaScript('window.__testSuccess')