Add support for Flash Player Component updates on Linux

chrome/common/component_flash_hint_file.h

+// Copyright 2015 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_COMPONENT_FLASH_HINT_FILE_H_
+#define CHROME_COMMON_COMPONENT_FLASH_HINT_FILE_H_
+
+#include <string>
+#include <vector>
+
+#include "base/files/file_util.h"
+#include "crypto/secure_hash.h"
+
+namespace chrome {
+
+// This class wraps the component updated flash hint file, which lives inside
+// the PepperFlash folder of  the user-data-dir, so that the Linux zygote
+// process can preload the right version of flash.
+class ComponentFlashHintFile {

[jln (very slow on Chromium), 2015/08/06 18:48:14]

This class has only static members. You may want to consider using a namespace
instead:

http://google-styleguide.googlecode.com/svn/trunk/cppguide.html#Nonmember,_St...

But grouping in classes is common.

[Greg K, 2015/08/07 21:15:29]

Done.

+ public:
+  // Records a new flash update into the hint file.
+  // unpacked_plugin is the current location of the plugin.

[jln (very slow on Chromium), 2015/08/06 18:48:14]

Use |argument| to document argument "argument".

[Greg K, 2015/08/07 21:15:28]

Done.

+  // moved_plugin is the location where the plugin will be loaded from.
+  static bool RecordFlashUpdate(const base::FilePath& unpacked_plugin,
+                                const base::FilePath& moved_plugin,
+                                const std::string& version);
+  // Reports whether or not a hints file exists.
+  static bool DoesHintFileExist();
+  // Return the path of the component updated flash plugin, only if the file has
+  // the correct hash sum.

[jln (very slow on Chromium), 2015/08/06 18:48:14]

Mention and document both arguments.

[Greg K, 2015/08/07 21:15:29]

Done.

+  static bool VerifyAndReturnFlashLocation(base::FilePath* path,
+                                           std::string* version);
+
+  // Test if the specified plugin file can be mapped executable.
+  // This is useful to test if the flash plugin is in a directory mounted
+  // NOEXEC.

[jln (very slow on Chromium), 2015/08/06 18:48:14]

nit: "noexec". Explain why this matters.

See my other remark in the caller: why is it useful to treat this failure in a
special way? We don't seem to be providing any helpful error message.

[Greg K, 2015/08/07 21:15:28]

It's useful so that Chrome can fall back to the bundled flash plugin. Indeed, I
added an error message where this is called. And I have explained the function
in the comment.

+  static bool TestExecutableMapping(const base::FilePath& path);
+
+ private:
+  // This will serialize the file to disk as JSON. The format is:
+  // {
+  //  "Version": 0x10,
+  //  "HashAlgorithm": SecureHash::SHA256,
+  //  "Hash": <Base64 Encoded Hash>,
+  //  "PluginPath": /path/to/component/updated/flash.so,
+  //  "PluginVersion": "1.0.0.1"
+  //  }
+  static bool WriteToDisk(const int version,
+                          const crypto::SecureHash::Algorithm algorithm,
+                          const std::string& hash,
+                          const base::FilePath& plugin_path,
+                          const std::string& flash_version);
+  DISALLOW_IMPLICIT_CONSTRUCTORS(ComponentFlashHintFile);
+};
+
+}  // namespace chrome
+
+#endif  // CHROME_COMMON_COMPONENT_FLASH_HINT_FILE_H_