Mac: Fix over-saturated colors on P3 displays (e.g. the 2016 MBPs).

src/video/cocoa/SDL_cocoawindow.m

@@ -1276,6 +1276,13 @@ Cocoa_CreateWindow(_THIS, SDL_Window * window)
     [nswindow setContentView:contentView];
     [contentView release];
 
+    /* The app's content is likely authored expecting sRGB output. If we don't
+     * specify the window's color space, it will default to the device color
+     * space, which will be P3 on capable displays. The mismatch causes the
+     * content authored in sRGB to appear extremely saturated on the P3 display.
+     */
+    [nswindow setColorSpace:[NSColorSpace sRGBColorSpace]];
+
     /* Allow files and folders to be dragged onto the window by users */
     [nswindow registerForDraggedTypes:[NSArray arrayWithObject:(NSString *)kUTTypeFileURL]];