nearby: snapshot as of cl/296436629

Signed-off-by: Alexey Polyudov <apolyudov@google.com>
Change-Id: I2cf5bf225b76f4c1541954651f3a7544a14e0cec

cpp/platform/api/system_clock.h

@@ -0,0 +1,22 @@
+#ifndef PLATFORM_API_SYSTEM_CLOCK_H_
+#define PLATFORM_API_SYSTEM_CLOCK_H_
+
+#include <cstdint>
+
+namespace location {
+namespace nearby {
+
+class SystemClock {
+ public:
+  virtual ~SystemClock() {}
+
+  // 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.
+  virtual std::int64_t elapsedRealtime() = 0;
+};
+
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_API_SYSTEM_CLOCK_H_