kiosk: Flush installed app files and cached crx

So that they don't get corrupted after unclean shutdown.
- Update UseSafeInstallation to enable flush in kiosk mode;
- Added a |flush_on_put_| bool to ExternalCache and make it
  flush cached crx when the bool is set;
- Update KioskAppManager to set the bool flag when
  initializing its ExternalCache;

BUG=555220

Review URL: https://codereview.chromium.org/1448723002

Cr-Commit-Position: refs/heads/master@{#360142}

chrome/browser/chromeos/app_mode/kiosk_app_manager.cc

@@ -562,6 +562,7 @@ KioskAppManager::KioskAppManager()
                         this,
                         true /* always_check_updates */,
                         false /* wait_for_cache_initialization */));
+  external_cache_->set_flush_on_put(true);
   UpdateAppData();
   local_accounts_subscription_ =
       CrosSettings::Get()->AddSettingsObserver(

chrome/browser/chromeos/app_mode/startup_app_launcher.cc

@@ -34,6 +34,7 @@
 #include "extensions/browser/extension_system.h"
 #include "extensions/common/constants.h"
 #include "extensions/common/extension.h"
+#include "extensions/common/file_util.h"
 #include "extensions/common/manifest_handlers/kiosk_mode_info.h"
 #include "extensions/common/manifest_handlers/offline_enabled_info.h"
 #include "extensions/common/manifest_url_handlers.h"
@@ -435,6 +436,7 @@ void StartupAppLauncher::OnLaunchFailure(KioskAppLaunchError::Error error) {
 }
 
 void StartupAppLauncher::BeginInstall() {
+  extensions::file_util::SetUseSafeInstallation(true);
   KioskAppManager::Get()->InstallFromCache(app_id_);
   if (extensions::ExtensionSystem::Get(profile_)
           ->extension_service()

chrome/browser/chromeos/extensions/external_cache.cc

@@ -28,6 +28,16 @@
 
 namespace chromeos {
 
+namespace {
+
+void FlushFile(const base::FilePath& path) {
+  base::File file(path, base::File::FLAG_OPEN | base::File::FLAG_WRITE);
+  file.Flush();
+  file.Close();
+}
+
+}  // namespace
+
 ExternalCache::ExternalCache(const base::FilePath& cache_dir,
                              net::URLRequestContextGetter* request_context,
                              const scoped_refptr<base::SequencedTaskRunner>&
@@ -320,6 +330,11 @@ void ExternalCache::OnPutExtension(const std::string& id,
     return;
   }
 
+  if (flush_on_put_) {
+    backend_task_runner_->PostTask(FROM_HERE,
+                                   base::Bind(&FlushFile, file_path));
+  }
+
   std::string update_url;
   if (entry->GetString(extensions::ExternalProviderImpl::kExternalUpdateUrl,
                        &update_url) &&

chrome/browser/chromeos/extensions/external_cache.h

@@ -134,6 +134,8 @@ class ExternalCache : public content::NotificationObserver,
                             const std::string& version,
                             const PutExternalExtensionCallback& callback);
 
+  void set_flush_on_put(bool flush_on_put) { flush_on_put_ = flush_on_put; }
+
  private:
   // Notifies the that the cache has been updated, providing
   // extensions loader with an updated list of extensions.
@@ -171,6 +173,9 @@ class ExternalCache : public content::NotificationObserver,
   // Set to true if cache should wait for initialization flag file.
   bool wait_for_cache_initialization_;
 
+  // Whether to flush the crx file after putting into |local_cache_|.
+  bool flush_on_put_ = false;
+
   // This is the list of extensions currently configured.
   scoped_ptr<base::DictionaryValue> extensions_;
 

extensions/common/file_util.cc

@@ -45,6 +45,13 @@ namespace extensions {
 namespace file_util {
 namespace {
 
+enum SafeInstallationFlag {
+  DEFAULT,   // Default case, controlled by a field trial.
+  DISABLED,  // Safe installation is disabled.
+  ENABLED,   // Safe installation is enabled.
+};
+SafeInstallationFlag g_use_safe_installation = DEFAULT;
+
 // Returns true if the given file path exists and is not zero-length.
 bool ValidateFilePath(const base::FilePath& path) {
   int64 size = 0;
@@ -97,6 +104,10 @@ void FlushFilesInDir(const base::FilePath& path,
 
 const base::FilePath::CharType kTempDirectoryName[] = FILE_PATH_LITERAL("Temp");
 
+void SetUseSafeInstallation(bool use_safe_installation) {
+  g_use_safe_installation = use_safe_installation ? ENABLED : DISABLED;
+}
+
 base::FilePath InstallExtension(const base::FilePath& unpacked_source_dir,
                                 const std::string& id,
                                 const std::string& version,

extensions/common/file_util.h

@@ -31,6 +31,9 @@ namespace file_util {
 
 extern const base::FilePath::CharType kTempDirectoryName[];
 
+// Sets the flag to enable safe installation (i.e. flush all installed files).
+void SetUseSafeInstallation(bool use_safe_installation);
+
 // Copies |unpacked_source_dir| into the right location under |extensions_dir|.
 // The destination directory is returned on success, or empty path is returned
 // on failure.