A bunch of remaining parts of extension content verification (Reland)

-The real guts of content_hash_fetcher.cc, which fetches the
 verified_contents.json file from the webstore if needed and also runs
 tasks to compute and cache the block-level hashes of all files in an
 extension.

-The real guts of content_hash_reader.cc, which uses the work done by
 the content_hash_fetcher during validation of extension file content as
 it's read off of disk at time of use.

-Code to avoid verifying transcoded files (images used in browser
 process, and message catalogs).

-Don't allow downgrade of mode via kForceFieldTrials command line switch

-Various bits of plumbing to support all of the above

This is a re-land with fixes; original review was:
  https://codereview.chromium.org/289533003

BUG=369895,373854
R=rockot@chromium.org

Review URL: https://codereview.chromium.org/288273004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@270937 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 64 insertions, 0 deletions

diff --git a/extensions/browser/computed_hashes.h b/extensions/browser/computed_hashes.h
new file mode 100644
index 0000000..c68175c
--- /dev/null
+++ b/extensions/browser/computed_hashes.h
@@ -0,0 +1,64 @@
+// Copyright 2014 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 EXTENSIONS_BROWSER_COMPUTED_HASHES_H_
+#define EXTENSIONS_BROWSER_COMPUTED_HASHES_H_
+
+#include <map>
+#include <string>
+#include <vector>
+
+#include "base/values.h"
+
+namespace base {
+class FilePath;
+}
+
+namespace extensions {
+
+// A pair of classes for serialization of a set of SHA256 block hashes computed
+// over the files inside an extension.
+class ComputedHashes {
+ public:
+  class Reader {
+   public:
+    Reader();
+    ~Reader();
+    bool InitFromFile(const base::FilePath& path);
+
+    // The block size and hashes for |relative_path| will be copied into the
+    // out parameters.
+    bool GetHashes(const base::FilePath& relative_path,
+                   int* block_size,
+                   std::vector<std::string>* hashes);
+
+   private:
+    typedef std::pair<int, std::vector<std::string> > HashInfo;
+
+    // This maps a relative path to a pair of (block size, hashes)
+    std::map<base::FilePath, HashInfo> data_;
+  };
+
+  class Writer {
+   public:
+    Writer();
+    ~Writer();
+
+    // Adds hashes for |relative_path|. Should not be called more than once
+    // for a given |relative_path|.
+    void AddHashes(const base::FilePath& relative_path,
+                   int block_size,
+                   const std::vector<std::string>& hashes);
+
+    bool WriteToFile(const base::FilePath& path);
+
+   private:
+    // The top-level object that will be serialized as JSON.
+    base::ListValue file_list_;
+  };
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_BROWSER_COMPUTED_HASHES_H_