Use valid /prefetch arguments for process launches on Windows. - do not submit

chrome/common/prefetch_argument_win.h

Index: chrome/common/prefetch_argument_win.h
diff --git a/chrome/common/prefetch_argument_win.h b/chrome/common/prefetch_argument_win.h
new file mode 100644
index 0000000000000000000000000000000000000000..1b3c32ca886401645ed208f632d019cf26646fb9
--- /dev/null
+++ b/chrome/common/prefetch_argument_win.h
@@ -0,0 +1,25 @@
+// Copyright (c) 2016 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.
+
+#ifndef CHROME_COMMON_PREFETCH_ARGUMENT_WIN_H_
+#define CHROME_COMMON_PREFETCH_ARGUMENT_WIN_H_
+
+namespace base {
+class CommandLine;
+}  // namespace base
+
+namespace chrome {
+// Adds a prefetch argument to |command_line|. The --type and
+// --no-startup-window switches must already have been added, if applicable, as
+// they determine which prefetch argument is added to |command_line|. It has
+// been observed that when file reads are consistent for 3 process launches with
+// the same prefetch argument, the prefetcher starts issuing the reads in batch
+// at process launch. This is more efficient than reading a few pages at a time
+// on-demand. The prefetcher isn't able to observe consistent file reads across
+// Chrome process launches when no prefetch argument is used, because the reads
+// depend on the process type.
+void AddWindowsPrefetchArgument(base::CommandLine* command_line);
+}  // namespace chrome
+
+#endif  // CHROME_COMMON_PREFETCH_ARGUMENT_WIN_H_