Taplog: print the touch's UIGestureRecognizers

Summary:
I think more information here will make everyone's lives easier while debugging!

It's common for gesture recognizers to preempt or otherwise interfere with a hit-testing view's touch handling:
- A UIScrollView can delay touches began (and does so with a private GR)
- A Tap GR on the target view or its superview can handle a touch and prevent touchesBegain from ever getting called on the hit-testing view (e.g. before the `delaysTouchesBegain` delay expires)
- A hit-testing UIButton (and only a UIButton) can cause a tap gesture recognizer to fail

etc.

Maybe we can also follow up with a mechanism for breaking when a given GR's state changes. But in the meantime it'd at least be helpful to add a watch expression and inspect a given GR manually.

Reviewed By: samishchandra

Differential Revision: D20908394

fbshipit-source-id: 89d075cc4073573013ef5fe41ebcaa026a77e2e5

Author: jballer

commands/FBFindCommands.py

@@ -120,6 +120,11 @@ def run(self, arguments, options):
   @staticmethod
   def taplog_callback(frame, bp_loc, internal_dict):
     parameterExpr = objc.functionPreambleExpressionForObjectParameterAtIndex(0)
-    print(fb.describeObject('[[[%s allTouches] anyObject] view]' % (parameterExpr)))
+    print('Gesture Recognizers:\n{}'.format(fb.describeObject(
+        '[[[%s allTouches] anyObject] gestureRecognizers]' % (parameterExpr)
+    )))
+    print('View:\n{}'.format(fb.describeObject(
+        '[[[%s allTouches] anyObject] view]' % (parameterExpr)
+    )))
     # We don't want to proceed event (click on button for example), so we just skip it
     lldb.debugger.HandleCommand('thread return')