Prepare ExternalPolicyDataUpdater and ResourceCache for blocking pool

chrome/browser/policy/cloud/resource_cache.cc

 // Copyright (c) 2013 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 "chrome/browser/policy/cloud/resource_cache.h"
 
 #include "base/base64.h"
 #include "base/file_util.h"
 #include "base/files/file_enumerator.h"
 #include "base/logging.h"
+#include "base/sequenced_task_runner.h"
 #include "base/strings/string_util.h"
 
 namespace policy {
 
 namespace {
 
 // Verifies that |value| is not empty and encodes it into base64url format,
 // which is safe to use as a file name on all platforms.
 bool Base64Encode(const std::string& value, std::string* encoded) {
   DCHECK(!value.empty());
@@ skipping 25 matching lines @@
 // emtpy.
 bool Base64Decode(const std::string& encoded, std::string* value) {
   std::string buffer;
   ReplaceChars(encoded, "-", "+", &buffer);
   ReplaceChars(buffer, "_", "/", &buffer);
   return base::Base64Decode(buffer, value) && !value->empty();
 }
 
 }  // namespace
 
-ResourceCache::ResourceCache(const base::FilePath& cache_dir)
-    : cache_dir_(cache_dir) {
-  // Allow the cache to be created in a different thread than the thread that is
-  // going to use it.
-  DetachFromThread();
+ResourceCache::ResourceCache(
+    const base::FilePath& cache_dir,
+    scoped_refptr<base::SequencedTaskRunner> task_runner)
+    : cache_dir_(cache_dir),
+      task_runner_(task_runner) {
 }
 
 ResourceCache::~ResourceCache() {
-  DCHECK(CalledOnValidThread());
+  DCHECK(task_runner_->RunsTasksOnCurrentThread());
 }
 
 bool ResourceCache::Store(const std::string& key,
                           const std::string& subkey,
                           const std::string& data) {
-  DCHECK(CalledOnValidThread());
+  DCHECK(task_runner_->RunsTasksOnCurrentThread());
   base::FilePath subkey_path;
   // Delete the file before writing to it. This ensures that the write does not
   // follow a symlink planted at |subkey_path|, clobbering a file outside the
   // cache directory. The mechanism is meant to foil file-system-level attacks
   // where a symlink is planted in the cache directory before Chrome has
   // started. An attacker controlling a process running concurrently with Chrome
   // would be able to race against the protection by re-creating the symlink
   // between these two calls. There is nothing in file_util that could be used
   // to protect against such races, especially as the cache is cross-platform
   // and therefore cannot use any POSIX-only tricks.
   return VerifyKeyPathAndGetSubkeyPath(key, true, subkey, &subkey_path) &&
          base::DeleteFile(subkey_path, false) &&
          file_util::WriteFile(subkey_path, data.data(), data.size());
 }
 
 bool ResourceCache::Load(const std::string& key,
                          const std::string& subkey,
                          std::string* data) {
-  DCHECK(CalledOnValidThread());
+  DCHECK(task_runner_->RunsTasksOnCurrentThread());
   base::FilePath subkey_path;
   // Only read from |subkey_path| if it is not a symlink.
   if (!VerifyKeyPathAndGetSubkeyPath(key, false, subkey, &subkey_path) ||
       file_util::IsLink(subkey_path)) {
     return false;
   }
   data->clear();
   return base::ReadFileToString(subkey_path, data);
 }
 
 void ResourceCache::LoadAllSubkeys(
     const std::string& key,
     std::map<std::string, std::string>* contents) {
-  DCHECK(CalledOnValidThread());
+  DCHECK(task_runner_->RunsTasksOnCurrentThread());
   contents->clear();
   base::FilePath key_path;
   if (!VerifyKeyPath(key, false, &key_path))
     return;
 
   base::FileEnumerator enumerator(key_path, false, base::FileEnumerator::FILES);
   for (base::FilePath path = enumerator.Next(); !path.empty();
        path = enumerator.Next()) {
     const std::string encoded_subkey = path.BaseName().MaybeAsASCII();
     std::string subkey;
     std::string data;
     // Only read from |subkey_path| if it is not a symlink and its name is
     // a base64-encoded string.
     if (!file_util::IsLink(path) &&
         Base64Decode(encoded_subkey, &subkey) &&
         base::ReadFileToString(path, &data)) {
       (*contents)[subkey].swap(data);
     }
   }
 }
 
 void ResourceCache::Delete(const std::string& key, const std::string& subkey) {
-  DCHECK(CalledOnValidThread());
+  DCHECK(task_runner_->RunsTasksOnCurrentThread());
   base::FilePath subkey_path;
   if (VerifyKeyPathAndGetSubkeyPath(key, false, subkey, &subkey_path))
     base::DeleteFile(subkey_path, false);
   // Delete() does nothing if the directory given to it is not empty. Hence, the
   // call below deletes the directory representing |key| if its last subkey was
   // just removed and does nothing otherwise.
   base::DeleteFile(subkey_path.DirName(), false);
 }
 
 void ResourceCache::PurgeOtherKeys(const std::set<std::string>& keys_to_keep) {
-  DCHECK(CalledOnValidThread());
+  DCHECK(task_runner_->RunsTasksOnCurrentThread());
   std::set<std::string> encoded_keys_to_keep;
   if (!Base64Encode(keys_to_keep, &encoded_keys_to_keep))
     return;
 
   base::FileEnumerator enumerator(
       cache_dir_, false, base::FileEnumerator::DIRECTORIES);
   for (base::FilePath path = enumerator.Next(); !path.empty();
        path = enumerator.Next()) {
     const std::string name(path.BaseName().MaybeAsASCII());
     if (encoded_keys_to_keep.find(name) == encoded_keys_to_keep.end())
       base::DeleteFile(path, true);
   }
 }
 
 void ResourceCache::PurgeOtherSubkeys(
     const std::string& key,
     const std::set<std::string>& subkeys_to_keep) {
-  DCHECK(CalledOnValidThread());
+  DCHECK(task_runner_->RunsTasksOnCurrentThread());
   base::FilePath key_path;
   if (!VerifyKeyPath(key, false, &key_path))
     return;
 
   std::set<std::string> encoded_subkeys_to_keep;
   if (!Base64Encode(subkeys_to_keep, &encoded_subkeys_to_keep))
     return;
 
   base::FileEnumerator enumerator(key_path, false, base::FileEnumerator::FILES);
   for (base::FilePath path = enumerator.Next(); !path.empty();
@@ skipping 28 matching lines @@
   if (!VerifyKeyPath(key, allow_create_key, &key_path) ||
       !Base64Encode(subkey, &encoded)) {
     return false;
   }
   *path = key_path.AppendASCII(encoded);
   return true;
 }
 
 
 }  // namespace policy