Revert the debugging changes that added vm abort flag and core dumps.

tools/bots/compiler.py

Index: tools/bots/compiler.py
diff --git a/tools/bots/compiler.py b/tools/bots/compiler.py
index 382646f997a95345da443dd60d87dad6adf8c8ad..a784a03ca7cf27c6848ad828d095c548c26e625e 100644
--- a/tools/bots/compiler.py
+++ b/tools/bots/compiler.py
@@ -20,7 +20,6 @@ import subprocess
 import sys
 
 import bot
-import bot_utils
 
 DARTIUM_BUILDER = r'none-dartium-(linux|mac|windows)'
 DART2JS_BUILDER = (
@@ -280,14 +279,12 @@ def TestCompiler(runtime, mode, system, flags, is_buildbot, arch,
   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')
-  unit_test_flags.append('--vm-options=--abort-on-assertion-errors')
   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.
-    with bot_utils.CoredumpEnabler():
-      TestStep("dart2js_unit", mode, system, 'none', 'vm', ['dart2js', 'try'],
-               unit_test_flags, arch)
+    TestStep("dart2js_unit", mode, system, 'none', 'vm', ['dart2js', 'try'],
+             unit_test_flags, arch)
 
   if compiler == 'dart2js' and runtime == 'drt':
     # Ensure that we run the "try" tests on Content Shell.