Switch all contexts in a share group to be on the same screen as the window they present to.

content/browser/renderer_host/compositing_iosurface_mac.h

Index: content/browser/renderer_host/compositing_iosurface_mac.h
diff --git a/content/browser/renderer_host/compositing_iosurface_mac.h b/content/browser/renderer_host/compositing_iosurface_mac.h
index 32743dc3117ea31da568e312c2a5d42f2989b8b6..19a04a6e75c7596c99b8abca552d609f57a035af 100644
--- a/content/browser/renderer_host/compositing_iosurface_mac.h
+++ b/content/browser/renderer_host/compositing_iosurface_mac.h
@@ -54,6 +54,9 @@ class CompositingIOSurfaceMac {
   void SetIOSurface(uint64 io_surface_handle,
                     const gfx::Size& size);
 
+  // Get the CGL renderer ID currently associated with this context.
+  int GetRendererID();
+
   // Blit the IOSurface at the upper-left corner of the |view|. If |view| window
   // size is larger than the IOSurface, the remaining right and bottom edges
   // will be white. |scaleFactor| is 1 in normal views, 2 in HiDPI views.