Add operator<< to ViewSnapshot

Author: wilhuff

Firestore/core/src/firebase/firestore/core/view_snapshot.h

@@ -22,6 +22,7 @@
 #endif  // !defined(__OBJC__)
 
 #include <functional>
+#include <iosfwd>
 #include <string>
 #include <utility>
 #include <vector>
@@ -177,6 +178,7 @@ class ViewSnapshot {
   }
 
   std::string ToString() const;
+  friend std::ostream& operator<<(std::ostream& out, const ViewSnapshot& value);
   size_t Hash() const;
 
  private:

Firestore/core/src/firebase/firestore/core/view_snapshot.mm

@@ -16,6 +16,8 @@
 
 #include "Firestore/core/src/firebase/firestore/core/view_snapshot.h"
 
+#include <ostream>
+
 #import "Firestore/Source/Core/FSTQuery.h"
 #import "Firestore/Source/Model/FSTDocument.h"
 #import "Firestore/Source/Model/FSTDocumentSet.h"
@@ -178,6 +180,10 @@
       mutated_keys().size(), sync_state_changed(), excludes_metadata_changes());
 }
 
+std::ostream& operator<<(std::ostream& out, const ViewSnapshot& value) {
+  return out << value.ToString();
+}
+
 size_t ViewSnapshot::Hash() const {
   // Note: We are omitting `mutated_keys_` from the hash, since we don't have a
   // straightforward way to compute its hash value. Since `ViewSnapshot` is