Update base::BindBlock for three parameters.

base/mac/bind_objc_block_unittest.mm

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "base/mac/bind_objc_block.h"
 
 #include <string>
 
 #include "base/callback.h"
 #include "base/bind.h"
@@ skipping 46 matching lines @@
   std::string result;
   std::string* ptr = &result;
   base::Callback<void(const std::string&, const std::string&)> c =
       base::BindBlock(^(const std::string& a, const std::string& b) {
           *ptr = a + b;
       });
   c.Run("forty", "two");
   EXPECT_EQ(result, "fortytwo");
 }
 
+TEST(BindObjcBlockTest, TestThreeArguments) {
+  std::string result;
+  std::string* ptr = &result;
+  base::Callback<void(const std::string&,
+                      const std::string&,
+                      const std::string&)> c =
+      base::BindBlock(^(const std::string& a,
+                        const std::string& b,
+                        const std::string& c) {
+          *ptr = a + b + c;
+      });
+  c.Run("six", "times", "nine");
+  EXPECT_EQ(result, "sixtimesnine");
+}
+
 }  // namespace