Base: Implement TimeElapsed

Some instances of TimeInfo serve the sole purpose of measuring time
duration. Using system time is unfortunate as it returns wall clock,
which is not guaranteed to be monotonic. Replace such a usage with
the new TimeElapsed class based on steady clock.

src/Base/TimeInfo.h

@@ -94,6 +94,40 @@ public:
     }
 };  // class TimeInfo
 
+using Ticks = std::chrono::steady_clock;
+
+class TimeElapsed: public std::chrono::time_point<Ticks>
+{
+public:
+    TimeElapsed()
+    {
+        setCurrent();
+    }
+
+    TimeElapsed(const TimeElapsed&) = default;
+    TimeElapsed(TimeElapsed&&) = default;
+    ~TimeElapsed() = default;
+
+    void setCurrent()
+    {
+        static_cast<std::chrono::time_point<Ticks>&>(*this) = Ticks::now();
+    }
+
+    static float diffTimeF(const TimeElapsed& start, const TimeElapsed& end = TimeElapsed())
+    {
+        const std::chrono::duration<float> duration = end - start;
+        return duration.count();
+    }
+
+    static std::string diffTime(const TimeElapsed& start, const TimeElapsed& end = TimeElapsed())
+    {
+        std::stringstream ss;
+        const std::chrono::duration<float> secs = end - start;
+        ss << secs.count();
+        return ss.str();
+    }
+};  // class TimeElapsed
+
 }  // namespace Base
 
 #endif  // BASE_TIMEINFO_H