Use a valid /prefetch argument when launching a process.

chrome/app/prefetch_argument_win.cc

Index: chrome/app/prefetch_argument_win.cc
diff --git a/chrome/app/prefetch_argument_win.cc b/chrome/app/prefetch_argument_win.cc
new file mode 100644
index 0000000000000000000000000000000000000000..66d70536aa194356386bc8bade3221caebecf165
--- /dev/null
+++ b/chrome/app/prefetch_argument_win.cc
@@ -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.
+
+#include "base/command_line.h"
+#include "base/macros.h"
+#include "base/strings/string16.h"
+#include "base/strings/string_util.h"
+
+bool HasValidWindowsPrefetchArgument(const base::CommandLine& command_line) {

[gab, 2016/01/29 19:39:28]

This is only used for a DCHECK, how about moving it to an anonymous method in
that file?

[fdoray, 2016/02/01 13:28:26]

Done.

+  const base::char16 kPrefetchArgumentPrefix[] = L"/prefetch:";
+
+  // Check if |command_line| contains an argument "/prefetch:#" where # is
+  // [1, 8].
+  for (const auto& arg : command_line.argv()) {
+    if (arg.size() == arraysize(kPrefetchArgumentPrefix) &&
+        base::StartsWith(arg, kPrefetchArgumentPrefix,
+                         base::CompareCase::SENSITIVE) &&
+        arg[arraysize(kPrefetchArgumentPrefix) - 1] >= L'1' &&

[gab, 2016/01/29 19:39:28]

return arg[arraysize(kPrefetchArgumentPrefix) - 1] >= L'1' &&
arg[arraysize(kPrefetchArgumentPrefix) - 1] >= L'1' &&;

(i.e. if we find an arg that matches but isn't 1-8, we shouldn't keep looking)

[fdoray, 2016/02/01 13:28:26]

Done.

+        arg[arraysize(kPrefetchArgumentPrefix) - 1] <= L'8') {
+      return true;
+    }
+  }
+  return false;
+}