diff --git a/tools/gn/filesystem_utils.cc b/tools/gn/filesystem_utils.cc
index 2ceca81..5905cdb 100644
--- a/tools/gn/filesystem_utils.cc
+++ b/tools/gn/filesystem_utils.cc
@@ -687,86 +687,6 @@
   return toolchain_label.name() + "/";
 }
 
-bool ContentsEqual(const base::FilePath& file_path, const std::string& data) {
-  // Compare file and stream sizes first. Quick and will save us some time if
-  // they are different sizes.
-  int64_t file_size;
-  if (!base::GetFileSize(file_path, &file_size) ||
-      static_cast<size_t>(file_size) != data.size()) {
-    return false;
-  }
-
-  std::string file_data;
-  file_data.resize(file_size);
-  if (!base::ReadFileToString(file_path, &file_data))
-    return false;
-
-  return file_data == data;
-}
-
-bool WriteFileIfChanged(const base::FilePath& file_path,
-                        const std::string& data,
-                        Err* err) {
-  if (ContentsEqual(file_path, data))
-    return true;
-
-  // Create the directory if necessary.
-  if (!base::CreateDirectory(file_path.DirName())) {
-    if (err) {
-      *err =
-          Err(Location(), "Unable to create directory.",
-              "I was using \"" + FilePathToUTF8(file_path.DirName()) + "\".");
-    }
-    return false;
-  }
-
-  int size = static_cast<int>(data.size());
-  bool write_success = false;
-
-#if defined(OS_WIN)
-  // On Windows, provide a custom implementation of base::WriteFile. Sometimes
-  // the base version fails, especially on the bots. The guess is that Windows
-  // Defender or other antivirus programs still have the file open (after
-  // checking for the read) when the write happens immediately after. This
-  // version opens with FILE_SHARE_READ (normally not what you want when
-  // replacing the entire contents of the file) which lets us continue even if
-  // another program has the file open for reading. See http://crbug.com/468437
-  base::win::ScopedHandle file(::CreateFile(file_path.value().c_str(),
-                                            GENERIC_WRITE, FILE_SHARE_READ,
-                                            NULL, CREATE_ALWAYS, 0, NULL));
-  if (file.IsValid()) {
-    DWORD written;
-    BOOL result = ::WriteFile(file.Get(), data.c_str(), size, &written, NULL);
-    if (result) {
-      if (static_cast<int>(written) == size) {
-        write_success = true;
-      } else {
-        // Didn't write all the bytes.
-        LOG(ERROR) << "wrote" << written << " bytes to "
-                   << base::UTF16ToUTF8(file_path.value()) << " expected "
-                   << size;
-      }
-    } else {
-      // WriteFile failed.
-      PLOG(ERROR) << "writing file " << base::UTF16ToUTF8(file_path.value())
-                  << " failed";
-    }
-  } else {
-    PLOG(ERROR) << "CreateFile failed for path "
-                << base::UTF16ToUTF8(file_path.value());
-  }
-#else
-  write_success = base::WriteFile(file_path, data.c_str(), size) == size;
-#endif
-
-  if (!write_success && err) {
-    *err = Err(Location(), "Unable to write file.",
-               "I was writing \"" + FilePathToUTF8(file_path) + "\".");
-  }
-
-  return write_success;
-}
-
 SourceDir GetToolchainOutputDir(const Settings* settings) {
   return settings->toolchain_output_subdir().AsSourceDir(
       settings->build_settings());
diff --git a/tools/gn/filesystem_utils.h b/tools/gn/filesystem_utils.h
index aaa08ba..f64c00d 100644
--- a/tools/gn/filesystem_utils.h
+++ b/tools/gn/filesystem_utils.h
@@ -163,18 +163,6 @@
 // go in the root build directory. Otherwise, the result will end in a slash.
 std::string GetOutputSubdirName(const Label& toolchain_label, bool is_default);
 
-// Returns true if the contents of the file and stream given are equal, false
-// otherwise.
-bool ContentsEqual(const base::FilePath& file_path, const std::string& data);
-
-// Writes given stream contents to the given file if it differs from existing
-// file contents. Returns true if new contents was successfully written or
-// existing file contents doesn't need updating, false on write error. |err| is
-// set on write error if not nullptr.
-bool WriteFileIfChanged(const base::FilePath& file_path,
-                        const std::string& data,
-                        Err* err);
-
 // -----------------------------------------------------------------------------
 
 // These functions return the various flavors of output and gen directories.
diff --git a/tools/gn/filesystem_utils_unittest.cc b/tools/gn/filesystem_utils_unittest.cc
index e44d337..27ccab2 100644
--- a/tools/gn/filesystem_utils_unittest.cc
+++ b/tools/gn/filesystem_utils_unittest.cc
@@ -3,11 +3,8 @@
 // found in the LICENSE file.
 
 #include "base/files/file_path.h"
-#include "base/files/file_util.h"
-#include "base/files/scoped_temp_dir.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
-#include "base/threading/platform_thread.h"
 #include "build/build_config.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "tools/gn/filesystem_utils.h"
@@ -557,59 +554,6 @@
 #endif
 }
 
-TEST(FilesystemUtils, ContentsEqual) {
-  base::ScopedTempDir temp_dir;
-  ASSERT_TRUE(temp_dir.CreateUniqueTempDir());
-
-  std::string data = "foo";
-
-  base::FilePath file_path = temp_dir.path().AppendASCII("foo.txt");
-  base::WriteFile(file_path, data.c_str(), static_cast<int>(data.size()));
-
-  EXPECT_TRUE(ContentsEqual(file_path, data));
-
-  // Different length and contents.
-  data += "bar";
-  EXPECT_FALSE(ContentsEqual(file_path, data));
-
-  // The same length, different contents.
-  EXPECT_FALSE(ContentsEqual(file_path, "bar"));
-}
-
-TEST(FilesystemUtils, WriteFileIfChanged) {
-  base::ScopedTempDir temp_dir;
-  ASSERT_TRUE(temp_dir.CreateUniqueTempDir());
-
-  std::string data = "foo";
-
-  // Write if file doesn't exist. Create also directory.
-  base::FilePath file_path =
-      temp_dir.path().AppendASCII("bar").AppendASCII("foo.txt");
-  EXPECT_TRUE(WriteFileIfChanged(file_path, data, nullptr));
-
-  base::File::Info file_info;
-  ASSERT_TRUE(base::GetFileInfo(file_path, &file_info));
-  base::Time last_modified = file_info.last_modified;
-
-#if defined(OS_MACOSX)
-  // Modification times are in seconds in HFS on Mac.
-  base::TimeDelta sleep_time = base::TimeDelta::FromSeconds(1);
-#else
-  base::TimeDelta sleep_time = base::TimeDelta::FromMilliseconds(1);
-#endif
-  base::PlatformThread::Sleep(sleep_time);
-
-  // Don't write if contents is the same.
-  EXPECT_TRUE(WriteFileIfChanged(file_path, data, nullptr));
-  ASSERT_TRUE(base::GetFileInfo(file_path, &file_info));
-  EXPECT_EQ(last_modified, file_info.last_modified);
-
-  // Write if contents changed.
-  EXPECT_TRUE(WriteFileIfChanged(file_path, "bar", nullptr));
-  ASSERT_TRUE(base::GetFileInfo(file_path, &file_info));
-  EXPECT_NE(last_modified, file_info.last_modified);
-}
-
 TEST(FilesystemUtils, GetToolchainDirs) {
   BuildSettings build_settings;
   build_settings.SetBuildDir(SourceDir("//out/Debug/"));
diff --git a/tools/gn/function_write_file.cc b/tools/gn/function_write_file.cc
index feb1004..9159975 100644
--- a/tools/gn/function_write_file.cc
+++ b/tools/gn/function_write_file.cc
@@ -19,6 +19,55 @@
 
 namespace functions {
 
+namespace {
+
+// On Windows, provide a custom implementation of base::WriteFile. Sometimes
+// the base version fails, especially on the bots. The guess is that Windows
+// Defender or other antivirus programs still have the file open (after
+// checking for the read) when the write happens immediately after. This
+// version opens with FILE_SHARE_READ (normally not what you want when
+// replacing the entire contents of the file) which lets us continue even if
+// another program has the file open for reading. See http://crbug.com/468437
+#if defined(OS_WIN)
+int DoWriteFile(const base::FilePath& filename, const char* data, int size) {
+  base::win::ScopedHandle file(::CreateFile(
+      filename.value().c_str(),
+      GENERIC_WRITE,
+      FILE_SHARE_READ,
+      NULL,
+      CREATE_ALWAYS,
+      0,
+      NULL));
+  if (!file.IsValid()) {
+    PLOG(ERROR) << "CreateFile failed for path "
+                  << base::UTF16ToUTF8(filename.value());
+    return -1;
+  }
+
+  DWORD written;
+  BOOL result = ::WriteFile(file.Get(), data, size, &written, NULL);
+  if (result && static_cast<int>(written) == size)
+    return written;
+
+  if (!result) {
+    // WriteFile failed.
+    PLOG(ERROR) << "writing file " << base::UTF16ToUTF8(filename.value())
+                << " failed";
+  } else {
+    // Didn't write all the bytes.
+    LOG(ERROR) << "wrote" << written << " bytes to "
+               << base::UTF16ToUTF8(filename.value()) << " expected " << size;
+  }
+  return -1;
+}
+#else
+int DoWriteFile(const base::FilePath& filename, const char* data, int size) {
+  return base::WriteFile(filename, data, size);
+}
+#endif
+
+}  // namespace
+
 const char kWriteFile[] = "write_file";
 const char kWriteFile_HelpShort[] =
     "write_file: Write a file to disk.";
@@ -89,14 +138,30 @@
   } else {
     contents << args[1].ToString(false);
   }
-
+  const std::string& new_contents = contents.str();
   base::FilePath file_path =
       scope->settings()->build_settings()->GetFullPath(source_file);
 
   // Make sure we're not replacing the same contents.
-  if (!WriteFileIfChanged(file_path, contents.str(), err))
-    *err = Err(function->function(), err->message(), err->help_text());
+  std::string existing_contents;
+  if (base::ReadFileToString(file_path, &existing_contents) &&
+      existing_contents == new_contents)
+    return Value();  // Nothing to do.
 
+  // Write file, creating the directory if necessary.
+  if (!base::CreateDirectory(file_path.DirName())) {
+    *err = Err(function->function(), "Unable to create directory.",
+               "I was using \"" + FilePathToUTF8(file_path.DirName()) + "\".");
+    return Value();
+  }
+
+  int int_size = static_cast<int>(new_contents.size());
+  if (DoWriteFile(file_path, new_contents.c_str(), int_size)
+      != int_size) {
+    *err = Err(function->function(), "Unable to write file.",
+               "I was writing \"" + FilePathToUTF8(file_path) + "\".");
+    return Value();
+  }
   return Value();
 }
 
diff --git a/tools/gn/ninja_target_writer.cc b/tools/gn/ninja_target_writer.cc
index 9f19b2b..7d9c08a 100644
--- a/tools/gn/ninja_target_writer.cc
+++ b/tools/gn/ninja_target_writer.cc
@@ -74,7 +74,9 @@
     CHECK(0) << "Output type of target not handled.";
   }
 
-  WriteFileIfChanged(ninja_file, file.str(), nullptr);
+  std::string contents = file.str();
+  base::WriteFile(ninja_file, contents.c_str(),
+                  static_cast<int>(contents.size()));
 }
 
 void NinjaTargetWriter::WriteEscapedSubstitution(SubstitutionType type) {
diff --git a/tools/gn/visual_studio_writer.cc b/tools/gn/visual_studio_writer.cc
index dec0837..44a3f11 100644
--- a/tools/gn/visual_studio_writer.cc
+++ b/tools/gn/visual_studio_writer.cc
@@ -9,6 +9,7 @@
 #include <set>
 #include <string>
 
+#include "base/files/file_util.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/string_util.h"
@@ -152,6 +153,26 @@
   return base::StringPiece();
 }
 
+bool HasSameContent(std::stringstream& data_1, const base::FilePath& data_2) {
+  // Compare file sizes first. Quick and will save us some time if they are
+  // different sizes.
+  int64_t data_1_len = data_1.tellp();
+
+  int64_t data_2_len;
+  if (!base::GetFileSize(data_2, &data_2_len) || data_1_len != data_2_len)
+    return false;
+
+  std::string data_2_data;
+  data_2_data.resize(data_2_len);
+  if (!base::ReadFileToString(data_2, &data_2_data))
+    return false;
+
+  std::string data_1_data;
+  data_1_data = data_1.str();
+
+  return data_1_data == data_2_data;
+}
+
 }  // namespace
 
 VisualStudioWriter::SolutionEntry::SolutionEntry(const std::string& _name,
@@ -268,13 +289,32 @@
   // Only write the content to the file if it's different. That is
   // both a performance optimization and more importantly, prevents
   // Visual Studio from reloading the projects.
-  if (!WriteFileIfChanged(vcxproj_path, vcxproj_string_out.str(), err))
-    return false;
+  if (!HasSameContent(vcxproj_string_out, vcxproj_path)) {
+    std::string content = vcxproj_string_out.str();
+    int size = static_cast<int>(content.size());
+    if (base::WriteFile(vcxproj_path, content.c_str(), size) != size) {
+      *err = Err(Location(), "Couldn't open " + target->label().name() +
+                                 ".vcxproj for writing");
+      return false;
+    }
+  }
 
   base::FilePath filters_path = UTF8ToFilePath(vcxproj_path_str + ".filters");
+
   std::stringstream filters_string_out;
   WriteFiltersFileContents(filters_string_out, target);
-  return WriteFileIfChanged(filters_path, filters_string_out.str(), err);
+
+  if (!HasSameContent(filters_string_out, filters_path)) {
+    std::string content = filters_string_out.str();
+    int size = static_cast<int>(content.size());
+    if (base::WriteFile(filters_path, content.c_str(), size) != size) {
+      *err = Err(Location(), "Couldn't open " + target->label().name() +
+                                 ".vcxproj.filters for writing");
+      return false;
+    }
+  }
+
+  return true;
 }
 
 bool VisualStudioWriter::WriteProjectFileContents(
@@ -572,7 +612,17 @@
   // Only write the content to the file if it's different. That is
   // both a performance optimization and more importantly, prevents
   // Visual Studio from reloading the projects.
-  return WriteFileIfChanged(sln_path, string_out.str(), err);
+  if (HasSameContent(string_out, sln_path))
+    return true;
+
+  std::string content = string_out.str();
+  int size = static_cast<int>(content.size());
+  if (base::WriteFile(sln_path, content.c_str(), size) != size) {
+    *err = Err(Location(), "Couldn't open all.sln for writing");
+    return false;
+  }
+
+  return true;
 }
 
 void VisualStudioWriter::WriteSolutionFileContents(