Revert of Enable isolate on Linux release builder.

scripts/slave/recipe_modules/chromium_tests/api.py

 # Copyright 2014 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.
 
 import copy
 
 from slave import recipe_api
 
 
 # Different types of builds this recipe module can do.
@@ skipping 219 matching lines @@
             compile_targets.update(test.compile_targets(self.m))
 
       self.m.chromium.compile(targets=sorted(compile_targets))
       self.m.chromium.checkdeps()
 
       if self.m.chromium.c.TARGET_PLATFORM == 'android':
         self.m.chromium_android.check_webview_licenses()
         self.m.chromium_android.findbugs()
 
       has_swarming_tests = any(t.uses_swarming for t in tests)
-      if has_swarming_tests:
+      if bot_config.get('use_isolate'):
+        self.m.isolate.find_isolated_tests(self.m.chromium.output_dir)
+      # TODO(phajdan.jr): Always use the below codepath once fully tested.
+      elif has_swarming_tests:
         isolated_targets = [t.name for t in tests if t.uses_swarming]
         self.m.isolate.find_isolated_tests(
             self.m.chromium.output_dir, targets=list(set(isolated_targets)))
 
     got_revision = update_step.presentation.properties['got_revision']
 
     if bot_type == 'builder':
       if mastername == 'chromium.linux':
         # TODO(samuong): This is restricted to Linux for now until I have more
         # confidence that it is not totally broken.
@@ skipping 63 matching lines @@
       self.m.chromium.crash_handler()
 
     try:
       return test_runner()
     finally:
       if self.m.platform.is_win:
         self.m.chromium.process_dumps()
 
       if self.m.chromium.c.TARGET_PLATFORM == 'android':
         self.m.chromium_android.common_tests_final_steps()