[POSIX] CHECK that pthread_join succeeds in PlatformThread::Join.

base/threading/platform_thread_posix.cc

Index: base/threading/platform_thread_posix.cc
diff --git a/base/threading/platform_thread_posix.cc b/base/threading/platform_thread_posix.cc
index 43a42eca98a3e25414ee2e5847d15ad5bbfb44a7..392d4613369bcb04a965225b344a371407e43b45 100644
--- a/base/threading/platform_thread_posix.cc
+++ b/base/threading/platform_thread_posix.cc
@@ -225,7 +225,7 @@ void PlatformThread::Join(PlatformThreadHandle thread_handle) {
   // the thread referred to by |thread_handle| may still be running long-lived /
   // blocking tasks.
   base::ThreadRestrictions::AssertIOAllowed();
-  pthread_join(thread_handle.handle_, NULL);
+  CHECK_EQ(0, pthread_join(thread_handle.handle_, NULL));
 }
 
 }  // namespace base