Fifo: Make g_bSkipCurrentFrame a TU-local variable

This is only ever queried, making it a global isn't necessary.

Source/Core/VideoCommon/BPStructs.cpp

@@ -380,7 +380,7 @@ static void BPWritten(const BPCmd& bp)
 	case BPMEM_CLEARBBOX2:
 		// Don't compute bounding box if this frame is being skipped!
 		// Wrong but valid values are better than bogus values...
-		if (!Fifo::g_bSkipCurrentFrame)
+		if (!Fifo::WillSkipCurrentFrame())
 		{
 			u8 offset = bp.address & 2;
 			BoundingBox::active = true;

Source/Core/VideoCommon/Fifo.cpp

@@ -33,7 +33,7 @@ namespace Fifo
 
 static constexpr u32 FIFO_SIZE = 2 * 1024 * 1024;
 
-bool g_bSkipCurrentFrame = false;
+static bool s_skip_current_frame = false;
 
 static Common::BlockingLoop s_gpu_mainloop;
 
@@ -82,7 +82,8 @@ void DoState(PointerWrap &p)
 		// We're good and paused, right?
 		s_video_buffer_seen_ptr = s_video_buffer_pp_read_ptr = s_video_buffer_read_ptr;
 	}
-	p.Do(g_bSkipCurrentFrame);
+
+	p.Do(s_skip_current_frame);
 	p.Do(s_last_sync_gpu_tick);
 }
 
@@ -129,7 +130,12 @@ void Shutdown()
 
 void SetRendering(bool enabled)
 {
-	g_bSkipCurrentFrame = !enabled;
+	s_skip_current_frame = !enabled;
+}
+
+bool WillSkipCurrentFrame()
+{
+	return s_skip_current_frame;
 }
 
 // May be executed from any thread, even the graphics thread.

Source/Core/VideoCommon/Fifo.h

@@ -13,8 +13,6 @@ class PointerWrap;
 namespace Fifo
 {
 
-extern bool g_bSkipCurrentFrame;
-
 // This could be in SConfig, but it depends on multiple settings
 // and can change at runtime.
 extern bool g_use_deterministic_gpu_thread;
@@ -53,5 +51,6 @@ void EmulatorState(bool running);
 bool AtBreakpoint();
 void ResetVideoBuffer();
 void SetRendering(bool bEnabled);
+bool WillSkipCurrentFrame();
 
-};
+} // namespace Fifo

Source/Core/VideoCommon/OpcodeDecoding.cpp

@@ -277,7 +277,7 @@ u8* Run(DataReader src, u32* cycles, bool in_display_list)
 					(cmd_byte & GX_PRIMITIVE_MASK) >> GX_PRIMITIVE_SHIFT,
 					num_vertices,
 					src,
-					Fifo::g_bSkipCurrentFrame,
+					Fifo::WillSkipCurrentFrame(),
 					is_preprocess);
 
 				if (bytes < 0)