Move C++ mu_guard class out of C-core public headers and fix style.
diff --git a/gRPC-Core.podspec b/gRPC-Core.podspec
index 1998bc8..146e5cc 100644
--- a/gRPC-Core.podspec
+++ b/gRPC-Core.podspec
@@ -208,6 +208,7 @@
'src/core/lib/gprpp/fork.h',
'src/core/lib/gprpp/manual_constructor.h',
'src/core/lib/gprpp/memory.h',
+ 'src/core/lib/gprpp/mutex_lock.h',
'src/core/lib/gprpp/thd.h',
'src/core/lib/profiling/timers.h',
'src/core/lib/gpr/alloc.cc',
@@ -844,6 +845,7 @@
'src/core/lib/gprpp/fork.h',
'src/core/lib/gprpp/manual_constructor.h',
'src/core/lib/gprpp/memory.h',
+ 'src/core/lib/gprpp/mutex_lock.h',
'src/core/lib/gprpp/thd.h',
'src/core/lib/profiling/timers.h',
'src/core/ext/transport/chttp2/transport/bin_decoder.h',