Enable only 'downloads' related tests in browser_tests on coverage bot.

tools/code_coverage/coverage_posix.py

 #!/usr/bin/env python
 # Copyright (c) 2012 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.
 
 """Generate and process code coverage.
 
 TODO(jrg): rename this from coverage_posix.py to coverage_all.py!
 
 Written for and tested on Mac, Linux, and Windows.  To use this script
@@ skipping 226 matching lines @@
          '*OldDetachedPanelBrowserTest.*',
          'PanelDragBrowserTest.AttachWithSqueeze',
          '*PanelBrowserTest.*',
          '*DockedPanelBrowserTest.*',
          '*DetachedPanelBrowserTest.*',),
     'automated_ui_tests':
         ('AutomatedUITest.TheOneAndOnlyTest',
          'AutomatedUITestBase.DragOut',), },
 }
 
+"""Since random tests are failing/hanging on coverage bot, we are enabling
+   tests feature by feature. crbug.com/159748
+   Below are the downloads related tests enabled.
+   SavePageBrowserTest.*
+   SavePageAsMHTMLBrowserTest.*
+   DownloadQueryTest.*
+   DownloadDangerPromptTest.*
+   DownloadTest.*
+"""
+gTestInclusions = {
+  'linux2': {
+    'browser_tests':
+        ('SavePageBrowserTest.*',
+         'SavePageAsMHTMLBrowserTest.*',
+         'DownloadQueryTest.*',
+         'DownloadDangerPromptTest.*',
+         'DownloadTest.*',),
+  },
+}
+
 
 def TerminateSignalHandler(sig, stack):
   """When killed, try and kill our child processes."""
   signal.signal(sig, signal.SIG_DFL)
   for pid in gChildPIDs:
     if 'kill' in os.__all__:  # POSIX
       os.kill(pid, sig)
     else:
       subprocess.call(['taskkill.exe', '/PID', str(pid)])
   sys.exit(0)
@@ skipping 519 matching lines @@
 
     if not self.options.no_exclusions:
       exclusions = excl or gTestExclusions
       excldict = exclusions.get(sys.platform)
       if excldict:
         for test in excldict.keys():
           # example: if base_unittests in ../blah/blah/base_unittests.exe
           if test in fulltest:
             negative_gfilter_list += excldict[test]
 
+    inclusions = gTestInclusions
+    include_dict = inclusions.get(sys.platform)
+    if include_dict:
+      for test in include_dict.keys():
+        if test in fulltest:
+          positive_gfilter_list += include_dict[test]
+
     fulltest_basename = os.path.basename(fulltest)
     if fulltest_basename in self.test_filters:
       specific_test_filters = self.test_filters[fulltest_basename].split('-')
       if len(specific_test_filters) > 2:
         logging.error('Multiple "-" symbols in filter list: %s' %
           self.test_filters[fulltest_basename])
         raise BadUserInput()
       if len(specific_test_filters) == 2:
         # Remove trailing ':'
         specific_test_filters[0] = specific_test_filters[0][:-1]
@@ skipping 344 matching lines @@
   if options.trim:
     coverage.TrimTests()
   coverage.RunTests()
   if options.genhtml:
     coverage.GenerateHtml()
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main())