GPU: Intercept writes to the VERTEX_END_GL register.

This is the register that gets written after a game calls DrawArrays().

We should collect all GPU state and draw using our graphics API here.

src/video_core/engines/maxwell_3d.h

@@ -32,7 +32,12 @@ public:
 
         union {
             struct {
-                INSERT_PADDING_WORDS(0x6C0);
+                INSERT_PADDING_WORDS(0x585);
+                struct {
+                    u32 vertex_end_gl;
+                    u32 vertex_begin_gl;
+                } draw;
+                INSERT_PADDING_WORDS(0x139);
                 struct {
                     u32 query_address_high;
                     u32 query_address_low;
@@ -61,6 +66,9 @@ private:
     /// Handles a write to the QUERY_GET register.
     void ProcessQueryGet();
 
+    /// Handles a write to the VERTEX_END_GL register, triggering a draw.
+    void DrawArrays();
+
     MemoryManager& memory_manager;
 };