Add logcats link in builbot page for android swarming tasks

scripts/slave/recipe_modules/chromium_tests/steps.py

Index: scripts/slave/recipe_modules/chromium_tests/steps.py
diff --git a/scripts/slave/recipe_modules/chromium_tests/steps.py b/scripts/slave/recipe_modules/chromium_tests/steps.py
index 3e55c4186348c49ea67187f583439ecf8c3f3cc8..832cab05a31ee80daa572621685f34b7cb1a9e73 100644
--- a/scripts/slave/recipe_modules/chromium_tests/steps.py
+++ b/scripts/slave/recipe_modules/chromium_tests/steps.py
@@ -5,7 +5,7 @@
 import datetime
 import re
 import string
-
+import urllib
 
 class Test(object):
   """
@@ -912,6 +912,23 @@ class SwarmingGTestTest(SwarmingTest):
           api, suffix,test_filter=test_filter)
     finally:
       step_result = api.step.active_result
+
+      # If Android swarming tasks, create link for unified logcats
+      # https://crbug.com/448050
+      if api.chromium.c.TARGET_PLATFORM == 'android':
+        for task in self._tasks.values():
+          if hasattr(task, 'trigger_output') and 'tasks' in task.trigger_output:

[martiniss, 2016/08/04 00:44:09]

If we don't have this, what do we do? Is it an error? I would think so, right?
We should handle that, and output something like "logcat missing, file a bug?"
or something. Does that make sense?

[nicholaslin, 2016/08/04 19:28:51]

Added in an additional check to make sure the logdog butler cipd package is
installed. If the butler package is present and there is an output I think its
safe to assume the task is written to logdog?

+            for test in task.trigger_output['tasks'].values():
+              task_id = test.get('task_id')
+              shard_index = test.get('shard_index')
+              if shard_index is not None and task_id is not None:
+                prefix = 'https://luci-logdog.appspot.com/v/?s='
+                suffix = '%s/%s/%s/%s/+/%s' % ('android', 'swarming', 'logcats',
+                                               task_id, 'unified_logcats')
+                step_result.presentation.links[('shard_index: %d logcats' %
+                                                shard_index)] = (
+                    prefix + urllib.quote_plus(suffix))
+
       # Only upload test results if we have gtest results.
       if (self._upload_test_results and
           hasattr(step_result, 'test_utils') and