Make base::ReadFileToString() return false on I/O error.

base/file_util_unittest.cc

 // 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.
 
 #include "build/build_config.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #include <shellapi.h>
 #include <shlobj.h>
@@ skipping 1994 matching lines @@
                      &exact_buffer[0],
                      static_cast<int>(exact_buffer.size())));
 }
 
 TEST_F(FileUtilTest, ReadFileToString) {
   const char kTestData[] = "0123";
   std::string data;
 
   FilePath file_path =
       temp_dir_.path().Append(FILE_PATH_LITERAL("ReadFileToStringTest"));
+  FilePath file_path_dangerous =
+      temp_dir_.path().Append(FILE_PATH_LITERAL("..")).
+      Append(temp_dir_.path().BaseName()).
+      Append(FILE_PATH_LITERAL("ReadFileToStringTest"));
 
+  // Create test file.
   ASSERT_EQ(4, WriteFile(file_path, kTestData, 4));
 
   EXPECT_TRUE(ReadFileToString(file_path, &data));
   EXPECT_EQ(kTestData, data);
 
   data = "temp";
   EXPECT_FALSE(ReadFileToString(file_path, &data, 0));
-  EXPECT_EQ(data.length(), 0u);
+  EXPECT_EQ(0u, data.length());
 
   data = "temp";
   EXPECT_FALSE(ReadFileToString(file_path, &data, 2));
   EXPECT_EQ("01", data);
 
   data.clear();
   EXPECT_FALSE(ReadFileToString(file_path, &data, 3));
   EXPECT_EQ("012", data);
 
   data.clear();
   EXPECT_TRUE(ReadFileToString(file_path, &data, 4));
   EXPECT_EQ("0123", data);
 
   data.clear();
   EXPECT_TRUE(ReadFileToString(file_path, &data, 6));
   EXPECT_EQ("0123", data);
 
   EXPECT_TRUE(ReadFileToString(file_path, NULL, 6));
 
   EXPECT_TRUE(ReadFileToString(file_path, NULL));
 
+  data = "temp";
+  EXPECT_FALSE(ReadFileToString(file_path_dangerous, &data));
+  EXPECT_EQ(0u, data.length());
+
+  // Delete test file.
   EXPECT_TRUE(base::DeleteFile(file_path, false));
 
   data = "temp";
   EXPECT_FALSE(ReadFileToString(file_path, &data));
-  EXPECT_EQ(data.length(), 0u);
+  EXPECT_EQ(0u, data.length());
 
   data = "temp";
   EXPECT_FALSE(ReadFileToString(file_path, &data, 6));
-  EXPECT_EQ(data.length(), 0u);
+  EXPECT_EQ(0u, data.length());
 }
 
 TEST_F(FileUtilTest, TouchFile) {
   FilePath data_dir =
       temp_dir_.path().Append(FILE_PATH_LITERAL("FilePathTest"));
 
   // Create a fresh, empty copy of this directory.
   if (PathExists(data_dir)) {
     ASSERT_TRUE(DeleteFile(data_dir, true));
   }
@@ skipping 488 matching lines @@
   // Trying to close it should crash. This is important for security.
   EXPECT_DEATH(CloseWithScopedFD(fds[1]), "");
 #endif
 }
 
 #endif  // defined(OS_POSIX)
 
 }  // namespace
 
 }  // namespace base