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.mm

Index: content/browser/renderer_host/compositing_iosurface_mac.mm
diff --git a/content/browser/renderer_host/compositing_iosurface_mac.mm b/content/browser/renderer_host/compositing_iosurface_mac.mm
index a300eeed9f73db0964f1c7332db41199fd5153a1..37ac4c9eb5b5da78e0791ae8fbe66a62df5ba1bf 100644
--- a/content/browser/renderer_host/compositing_iosurface_mac.mm
+++ b/content/browser/renderer_host/compositing_iosurface_mac.mm
@@ -4,6 +4,7 @@
 
 #include "content/browser/renderer_host/compositing_iosurface_mac.h"
 
+#include <OpenGL/CGLRenderers.h>
 #include <OpenGL/OpenGL.h>
 #include <vector>
 
@@ -318,6 +319,15 @@ void CompositingIOSurfaceMac::SetIOSurface(uint64 io_surface_handle,
   CGLSetCurrentContext(0);
 }
 
+int CompositingIOSurfaceMac::GetRenderer() {
+  GLint current_renderer_id = -1;
+  if (CGLGetParameter(cglContext_,
+                      kCGLCPCurrentRendererID,
+                      &current_renderer_id) == kCGLNoError)
+    return current_renderer_id & kCGLRendererIDMatchingMask;
+  return -1;
+}
+
 void CompositingIOSurfaceMac::DrawIOSurface(NSView* view, float scale_factor) {
   CGLSetCurrentContext(cglContext_);