Add custom Insights logging for Share Sheet launch, cancel, and post

Summary: Now that FBNativeDialogs is in, extend the Custom Insights logging introduced earlier tonight to Share Sheet operations.

Test Plan: Tested by invoking the share sheet and watching things go.  Hit what I think Jason described as a bug with loginType that's causing the share sheet display to fail, but worked around it for the testing.

Reviewers: jacl, clang

Reviewed By: jacl

CC: msdkexp@

Differential Revision: https://phabricator.fb.com/D583401

src/FBNativeDialogs.m

@@ -17,6 +17,7 @@
 #import "FBNativeDialogs.h"
 #import "FBSession.h"
 #import "FBError.h"
+#import "FBUtility.h"
 #import "Social/Social.h"
 
 @interface FBNativeDialogs ()
@@ -85,12 +86,18 @@ + (BOOL)presentShareDialogModallyFrom:(UIViewController*)viewController
     }
 
     [composeViewController setCompletionHandler:^(SLComposeViewControllerResult result) {
+        BOOL cancelled = (result == SLComposeViewControllerResultCancelled);
+        NSString *eventToLog = cancelled ? @"_shareSheetCancel" : @"_shareSheetPost";
+        [FBUtility logInsightsEvent:eventToLog session:session];
         if (handler) {
-            handler((result == SLComposeViewControllerResultDone) ?FBNativeDialogResultSucceeded : FBNativeDialogResultCancelled, nil);
+            handler(cancelled ? FBNativeDialogResultCancelled : FBNativeDialogResultSucceeded, nil);
         }
     }];
 
     [viewController presentModalViewController:composeViewController animated:YES];
+
+    [FBUtility logInsightsEvent:@"_shareSheetLaunch" session:session];
+
     return YES;
 }