Convert 0 and NULL to nullptr in components.

Steps to replicate:
1. Build clang-tidy and clang-apply-replacements as described here: https://chromium.googlesource.com/chromium/src/+/lkcr/docs/clang_tidy.md
2. Build targets necessary for the change in out/gn.
3. Generate the compilation database:
  tools/clang/scripts/generate_compdb.py -p out/gn > compile_commands.json
4. Run clang-tidy and apply replacements:
  cd out/gn && PATH_TO_RUN_CLANG_TIDY/run-clang-tidy.py -p ../../ -clang-tidy-binary PATH_TO_CLANG_TIDY_BINARY -clang-apply-replacements-binary PATH_TO_CLANG_APPLY_REPLACEMENTS_BINARY -checks=-*,modernize-use-nullptr -fix -j 8 DIR_TO_CONVERT

Bug: 403854, 776257
Change-Id: Ifd0c147ac6866beacffbddb0c56b20502cb4f127
Reviewed-on: https://chromium-review.googlesource.com/732308
Reviewed-by: Jochen Eisinger <[email protected]>
Commit-Queue: Ivan Kotenkov <[email protected]>
Cr-Commit-Position: refs/heads/master@{#511144}
diff --git a/components/component_updater/component_updater_service.cc b/components/component_updater/component_updater_service.cc
index 6f0f84d..b99e5ed 100644
--- a/components/component_updater/component_updater_service.cc
+++ b/components/component_updater/component_updater_service.cc
@@ -227,14 +227,14 @@
     const std::string& id) const {
   DCHECK(thread_checker_.CalledOnValidThread());
   const auto it(components_.find(id));
-  return it != components_.end() ? &(it->second) : NULL;
+  return it != components_.end() ? &(it->second) : nullptr;
 }
 
 const CrxUpdateItem* CrxUpdateService::GetComponentState(
     const std::string& id) const {
   DCHECK(thread_checker_.CalledOnValidThread());
   const auto it(component_states_.find(id));
-  return it != component_states_.end() ? &it->second : NULL;
+  return it != component_states_.end() ? &it->second : nullptr;
 }
 
 void CrxUpdateService::MaybeThrottle(const std::string& id,