Common: Implement WallClock Interface and implement a native clock for x64

src/common/wall_clock.h

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+// Copyright 2020 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <chrono>
+
+#include "common/common_types.h"
+
+namespace Common {
+
+class WallClock {
+public:
+    virtual std::chrono::nanoseconds GetTimeNS() = 0;
+    virtual std::chrono::microseconds GetTimeUS() = 0;
+    virtual std::chrono::milliseconds GetTimeMS() = 0;
+    virtual u64 GetClockCycles() = 0;
+    virtual u64 GetCPUCycles() = 0;
+
+    /// Tells if the wall clock, uses the host CPU's hardware clock
+    bool IsNative() const {
+        return is_native;
+    }
+
+protected:
+    WallClock(u64 emulated_cpu_frequency, u64 emulated_clock_frequency, bool is_native)
+        : emulated_cpu_frequency{emulated_cpu_frequency},
+          emulated_clock_frequency{emulated_clock_frequency}, is_native{is_native} {}
+
+    u64 emulated_cpu_frequency;
+    u64 emulated_clock_frequency;
+
+private:
+    bool is_native;
+};
+
+WallClock* CreateBestMatchingClock(u32 emulated_cpu_frequency, u32 emulated_clock_frequency);
+
+} // namespace Common