Make ThreadChecker zero-sized

base/threading/thread_checker_unittest.cc

Index: base/threading/thread_checker_unittest.cc
diff --git a/base/threading/thread_checker_unittest.cc b/base/threading/thread_checker_unittest.cc
index 96455e66c704efee659099ff6db2fd484b4b550e..baec975ca43a98d60626a3ac2d0fda01c6e830ee 100644
--- a/base/threading/thread_checker_unittest.cc
+++ b/base/threading/thread_checker_unittest.cc
@@ -6,11 +6,13 @@
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
+#include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/sequence_token.h"
 #include "base/test/test_simple_task_runner.h"
 #include "base/threading/simple_thread.h"
+#include "base/threading/thread_checker.h"
 #include "base/threading/thread_checker_impl.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -18,6 +20,18 @@
 namespace base {
 namespace {
 
+#if !DCHECK_IS_ON()
+class ClassWithThreadChecker {
+  BASE_EXPORT size_t SilenceUnusedWarnings() {
+    return x + (y.CalledOnValidThread() ? 1 : 0);
+  }
+  uint32_t x;
+  ThreadChecker y;
+};
+
+static_assert(sizeof(ClassWithThreadChecker) == sizeof(uint32_t), "ThreadCheckerShouldHaveZeroSize");
+#endif
+
 // A thread that runs a callback.
 class RunCallbackThread : public SimpleThread {
  public: