Fix js_to_cpp_unittest handling of null arrays.

mojo/apps/js/test/js_to_cpp_unittest.cc

 // Copyright 2014 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.
 
 #include "base/file_util.h"
 #include "base/files/file_path.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/strings/utf_string_conversions.h"
 #include "gin/public/isolate_holder.h"
@@ skipping 109 matching lines @@
       data_pipe_handle, buffer, &buffer_size, MOJO_READ_DATA_FLAG_NONE);
   EXPECT_EQ(MOJO_RESULT_OK, result);
   EXPECT_EQ(64u, buffer_size);
   for (int i = 0; i < 64; ++i) {
     EXPECT_EQ(i, buffer[i]);
   }
 }
 
 void CheckCorruptedString(const mojo::String& arg) {
   // The values don't matter so long as all accesses are within bounds.
-  std::string name = arg.To<std::string>();
-  for (size_t i = 0; i < name.length(); ++i)
-    g_waste_accumulator += name[i];
+  if (arg.is_null())
+    return;
+  for (size_t i = 0; i < arg.size(); ++i)
+    g_waste_accumulator += arg[i];
 }
 
 void CheckCorruptedStringArray(const mojo::Array<mojo::String>& string_array) {
+  if (string_array.is_null())
+    return;
   for (size_t i = 0; i < string_array.size(); ++i)
     CheckCorruptedString(string_array[i]);
 }
 
 // Base Provider implementation class. It's expected that tests subclass and
 // override the appropriate Provider functions. When test is done quit the
 // run_loop().
 class CppSideConnection : public js_to_cpp::CppSide {
  public:
   CppSideConnection() : run_loop_(NULL), js_side_(NULL) {
@@ skipping 197 matching lines @@
   if (IsRunningOnIsolatedBot())
     return;
 
   BitFlipCppSideConnection cpp_side_connection;
   RunTest("mojo/apps/js/test/js_to_cpp_unittest", &cpp_side_connection);
   EXPECT_TRUE(cpp_side_connection.DidSucceed());
 }
 
 }  // namespace js
 }  // namespace mojo