Enable post-compile test isolation for all CI builders.

scripts/slave/recipe_modules/chromium_tests/api.py

Index: scripts/slave/recipe_modules/chromium_tests/api.py
diff --git a/scripts/slave/recipe_modules/chromium_tests/api.py b/scripts/slave/recipe_modules/chromium_tests/api.py
index 36b47f1bc5b9e2c345ac00aea6883b0ed81fda02..630292546346cdda84ff88e9a9b5930e06a9e3b7 100644
--- a/scripts/slave/recipe_modules/chromium_tests/api.py
+++ b/scripts/slave/recipe_modules/chromium_tests/api.py
@@ -140,8 +140,7 @@ class ChromiumTestsApi(recipe_api.RecipeApi):
     self.m.chromium.c.gyp_env.GYP_DEFINES.update(
         bot_config.get('GYP_DEFINES', {}))
     if bot_config.get('use_isolate'):
-      self.m.isolate.set_isolate_environment(
-          self.m.chromium.c, mode=bot_config.get('isolation_mode', 'archive'))
+      self.m.isolate.set_isolate_environment(self.m.chromium.c, mode='prepare')
     for c in recipe_config.get('chromium_apply_config', []):
       self.m.chromium.apply_config(c)
     for c in bot_config.get('chromium_apply_config', []):
@@ -193,8 +192,7 @@ class ChromiumTestsApi(recipe_api.RecipeApi):
       enable_swarming = bot_config.get('enable_swarming')
 
     if enable_swarming:
-      self.m.isolate.set_isolate_environment(
-          self.m.chromium.c, mode=bot_config.get('isolation_mode', 'archive'))
+      self.m.isolate.set_isolate_environment(self.m.chromium.c, mode='prepare')
       self.m.swarming.check_client_version()
       self.m.swarming.default_priority = 50
       os_dimension = bot_config.get('swarming_dimensions', {}).get('os')
@@ -342,19 +340,12 @@ class ChromiumTestsApi(recipe_api.RecipeApi):
         self.m.chromium_android.findbugs()
 
       if isolated_targets:
-        isolation_mode = bot_config.get('isolation_mode', 'archive')
-        deduped_targets = list(set(isolated_targets))
-        # In 'archive' mode, 'compile' step does the archival, and we just need
-        # to find resulting *.isolated files.
-        if isolation_mode == 'archive':
-          self.m.isolate.find_isolated_tests(
-              self.m.chromium.output_dir, targets=deduped_targets)
-        else:
-          # In 'prepare' mode, 'compile' just prepares all information needed
-          # for isolation, and isolation is a separate step done here.
-          assert isolation_mode == 'prepare', isolation_mode
-          self.m.isolate.isolate_tests(
-              self.m.chromium.output_dir, targets=deduped_targets)
+        # In 'prepare' isolation mode, 'compile' just prepares all information
+        # needed for the isolation, and the isolation is a separate step.
+        self.m.isolate.isolate_tests(
+            self.m.chromium.output_dir,
+            targets=list(set(isolated_targets)),
+            verbose=True)
 
     got_revision = update_step.presentation.properties['got_revision']