Remove usage of CHECK_NOTNULL

We want to switch to absl logging instead of glog.  gtest and ceres are
going there, and we already have absl as a dependency.  ABSL doesn't
have CHECK_NOTNULL, and we can move things over in an easier to review
fashion.

Change-Id: Ifd9a11ec34a2357cec43f88dba015db9c28ed2cf
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/aos/events/logging/config_remapper.cc b/aos/events/logging/config_remapper.cc
index 21f45d5..088d393 100644
--- a/aos/events/logging/config_remapper.cc
+++ b/aos/events/logging/config_remapper.cc
@@ -263,7 +263,8 @@
   result.reserve(remapped_channels_.size());
   for (auto &pair : remapped_channels_) {
     const Channel *const original_channel =
-        CHECK_NOTNULL(original_configuration()->channels()->Get(pair.first));
+        original_configuration()->channels()->Get(pair.first);
+    CHECK(original_channel != nullptr);
 
     auto channel_iterator = std::lower_bound(
         remapped_configuration_->channels()->cbegin(),
@@ -472,9 +473,10 @@
 
   // Reconstruct the remapped channels.
   for (auto &pair : remapped_channels_) {
-    const Channel *const c = CHECK_NOTNULL(configuration::GetChannel(
+    const Channel *const c = configuration::GetChannel(
         base_config, original_configuration()->channels()->Get(pair.first), "",
-        nullptr));
+        nullptr);
+    CHECK(c != nullptr);
     channel_offsets.emplace_back(
         CopyChannel(c, pair.second.remapped_name, "", &fbb));