Cannot run incremental tests in checked mode, yet.

dart/tools/bots/compiler.py

Index: dart/tools/bots/compiler.py
diff --git a/dart/tools/bots/compiler.py b/dart/tools/bots/compiler.py
index 1a9b1199ffbf3019b8d356758f8a5a60b2f05a73..4f894bd6f1a6091d011b5db7e3875f58842ff978 100644
--- a/dart/tools/bots/compiler.py
+++ b/dart/tools/bots/compiler.py
@@ -270,17 +270,18 @@ def TestCompiler(runtime, mode, system, flags, is_buildbot, arch,
       # Failed to obtain version information. Continue running tests.
       pass
 
-  unit_test_flags = [flag for flag in flags if flag.startswith('--shard')]
-  # Run the unit tests in checked mode (the VM's checked mode).
-  unit_test_flags.append('--checked')
   if runtime == 'd8':
     # The dart2js compiler isn't self-hosted (yet) so we run its
     # unit tests on the VM. We avoid doing this on the builders
     # that run the browser tests to cut down on the cycle time.
+    unit_test_flags = [flag for flag in flags if flag.startswith('--shard')]
+    # Run the unit tests in checked mode (the VM's checked mode).
+    unit_test_flags.append('--checked')
     TestStep("dart2js_unit", mode, system, 'none', 'vm', ['dart2js', 'try'],
              unit_test_flags, arch)
 
   if compiler == 'dart2js' and runtime == 'drt':
+    unit_test_flags = [flag for flag in flags if flag.startswith('--shard')]
     # Ensure that we run the "try" tests on Content Shell.
     TestStep("incremental_compilation", mode, system, 'none', runtime,
              ['try'], unit_test_flags, arch)