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..1cda607c231a0fca72d875ab5e97858fe632f43c 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 +912,28 @@ 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

[ghost stip (do not use), 2016/08/04 23:55:58]

I wonder if there is a way to make this more generic so it's not just an android
specific hack. What I'm thinking about is a way to specify a 'link template' in
the buildbot json. We'd read that here and fill in the template if it exists.

'gtest_tests': [
  {
    'test': 'chrome_public_test_apk',
    'swarming': { blah },
    'post_run_links': {
      'shard_index: ${SHARD_INDEX} logcats':
'https://luci-logdog.appspot.com/v/android/swarming/logcats/${TASK_ID}/+/unified_logcats'
    }
  }
]

maybe that's too crazy though

[nicholaslin, 2016/08/05 00:27:17]

Perhaps. Maybe not a link template but maybe a logdog_url flag or something?
Then the android check can be replaced by a logdog_url check. Also we would no
longer have to check for cipd_packages.

+      # https://crbug.com/448050
+      if api.chromium.c.TARGET_PLATFORM == 'android':
+        for task in self._tasks.values():
+          includes_logdog = False
+          if hasattr(task, 'cipd_packages'):
+            func = lambda x: 'logdog/butler' in x[1]
+            includes_logdog = filter(func, task.cipd_packages)
+          if (includes_logdog and hasattr(task, 'trigger_output') 
+              and 'tasks' in task.trigger_output):
+            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