clang-tidy: Enforce google-global-names-in-headers

I remove the alias altogether because it appears inconsistent with the
style guide: "Don't put an alias in your public API just to save typing
in the implementation; do so only if you intend it to be used by your
clients." (https://google.github.io/styleguide/cppguide.html#Aliases).

Bug: 45
Change-Id: Ie9878250ca34387241d70d4261e9269147d8dcb6
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/68084
Reviewed-by: Ewout van Bekkum <ewout@google.com>
Commit-Queue: Ted Pudlik <tpudlik@google.com>
diff --git a/.clang-tidy b/.clang-tidy
index ca75a68..1a64978 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -23,6 +23,7 @@
     google-build-explicit-make-pair,
     google-build-namespaces,
     google-default-arguments,
+    google-global-names-in-headers,
     google-readability-function-size,
     google-readability-namespace-comments,
     google-runtime-operator,
diff --git a/pw_sync_stl/public/pw_sync_stl/counting_semaphore_inline.h b/pw_sync_stl/public/pw_sync_stl/counting_semaphore_inline.h
index 010a133..466b374 100644
--- a/pw_sync_stl/public/pw_sync_stl/counting_semaphore_inline.h
+++ b/pw_sync_stl/public/pw_sync_stl/counting_semaphore_inline.h
@@ -16,8 +16,6 @@
 #include "pw_chrono/system_clock.h"
 #include "pw_sync/counting_semaphore.h"
 
-using pw::chrono::SystemClock;
-
 namespace pw::sync {
 
 inline CountingSemaphore::CountingSemaphore()
@@ -26,9 +24,10 @@
 inline CountingSemaphore::~CountingSemaphore() {}
 
 inline bool CountingSemaphore::try_acquire_for(
-    chrono::SystemClock::duration timeout) {
+    pw::chrono::SystemClock::duration timeout) {
   // Due to spurious condition variable wakeups this cannot use wait_for().
-  return try_acquire_until(chrono::SystemClock::TimePointAfterAtLeast(timeout));
+  return try_acquire_until(
+      pw::chrono::SystemClock::TimePointAfterAtLeast(timeout));
 }
 
 inline CountingSemaphore::native_handle_type