nearby: snapshot of cl/304428753

Signed-off-by: Alexey Polyudov <apolyudov@google.com>
Change-Id: I0023ac6e40456fc4a8169c3173bcbff3b5ccc476

cpp/platform/api2/system_clock.h

@@ -0,0 +1,22 @@
+#ifndef PLATFORM_API2_SYSTEM_CLOCK_H_
+#define PLATFORM_API2_SYSTEM_CLOCK_H_
+
+#include <cstdint>
+
+#include "absl/time/time.h"
+
+namespace location {
+namespace nearby {
+
+class SystemClock final {
+ public:
+  // Returns the time (in milliseconds) since the system was booted, and
+  // includes deep sleep. This clock should be guaranteed to be monotonic, and
+  // should continue to tick even when the CPU is in power saving modes.
+  static absl::Time ElapsedRealtime();
+};
+
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_API2_SYSTEM_CLOCK_H_