Make SkOSWindow return the sample count and stencil bit count for its GL context.

experimental/iOSSampleApp/Shared/SkUIView.mm

Index: experimental/iOSSampleApp/Shared/SkUIView.mm
===================================================================
--- experimental/iOSSampleApp/Shared/SkUIView.mm	(revision 7991)
+++ experimental/iOSSampleApp/Shared/SkUIView.mm	(working copy)
@@ -93,6 +93,13 @@
     return false;
 }
 
+- (void)getAttachmentInfo:(SkOSWindow::AttachmentInfo*)info {
+    // we don't have a GL context.
+    info->fSampleCount = 0;
+    info->fStencilBits = 0;
+}
+
+
 #include "SkOSMenu.h"
 - (void)onAddMenu:(const SkOSMenu*)menu {
     [self.fOptionsDelegate view:self didAddMenu:menu];