Change FileStream to use FilePath instead of wstring.

net/base/file_stream_unittest.cc

Index: net/base/file_stream_unittest.cc
===================================================================
--- net/base/file_stream_unittest.cc	(revision 8584)
+++ net/base/file_stream_unittest.cc	(working copy)
@@ -19,16 +19,17 @@
     PlatformTest::SetUp();
 
     file_util::CreateTemporaryFileName(&temp_file_path_);
-    file_util::WriteFile(temp_file_path_, kTestData, kTestDataSize);
+    file_util::WriteFile(temp_file_path_.ToWStringHack(),
+                         kTestData, kTestDataSize);
   }
   virtual void TearDown() {
     file_util::Delete(temp_file_path_, false);
 
     PlatformTest::TearDown();
   }
-  const std::wstring temp_file_path() const { return temp_file_path_; }
+  const FilePath temp_file_path() const { return temp_file_path_; }
  private:
-  std::wstring temp_file_path_;
+  FilePath temp_file_path_;
 };
 
 TEST_F(FileStreamTest, BasicOpenClose) {