Clean up some grossness in ScrollResponder

Summary: Still gross but less gross.

Reviewed By: sebmarkbage

Differential Revision: D7107180

fbshipit-source-id: 31f1639a8f44e4ab247c338001a4a5c9b4b83cdf

Libraries/Components/TextInput/TextInputState.js

@@ -16,6 +16,8 @@
 const Platform = require('Platform');
 const UIManager = require('UIManager');
 
+const inputs = new Set();
+
 const TextInputState = {
    /**
    * Internal state
@@ -68,7 +70,19 @@ const TextInputState = {
         );
       }
     }
-  }
+  },
+
+  registerInput: function(textFieldID: number) {
+    inputs.add(textFieldID);
+  },
+
+  unregisterInput: function(textFieldID: number) {
+    inputs.delete(textFieldID);
+  },
+
+  isTextInput: function(textFieldID: number) {
+    return inputs.has(textFieldID);
+  },
 };
 
 module.exports = TextInputState;