Implement Dump-on-DCHECK (via a new LogSeverity).

base/task/cancelable_task_tracker_unittest.cc

Index: base/task/cancelable_task_tracker_unittest.cc
diff --git a/base/task/cancelable_task_tracker_unittest.cc b/base/task/cancelable_task_tracker_unittest.cc
index 01a1f23c8aa3c8c50ece1f7dcd3660ddfe91cad8..fd480f3687511a7fadbf13f5fc0f7014a9a5e7fe 100644
--- a/base/task/cancelable_task_tracker_unittest.cc
+++ b/base/task/cancelable_task_tracker_unittest.cc
@@ -15,6 +15,7 @@
 #include "base/memory/weak_ptr.h"
 #include "base/run_loop.h"
 #include "base/single_thread_task_runner.h"
+#include "base/test/gtest_util.h"
 #include "base/test/test_simple_task_runner.h"
 #include "base/threading/thread.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -348,11 +349,7 @@ class CancelableTaskTrackerDeathTest : public CancelableTaskTrackerTest {
 void MaybeRunDeadlyTaskTrackerMemberFunction(
     CancelableTaskTracker* task_tracker,
     const Callback<void(CancelableTaskTracker*)>& fn) {
-// CancelableTask uses DCHECKs with its ThreadChecker (itself only
-// enabled in debug mode).
-#if DCHECK_IS_ON()
-  EXPECT_DEATH_IF_SUPPORTED(fn.Run(task_tracker), "");
-#endif
+  EXPECT_DCHECK_DEATH(fn.Run(task_tracker));
 }
 
 void PostDoNothingTask(CancelableTaskTracker* task_tracker) {