Split TabRestoreService into InMemoryTRS and PersistentTRS

chrome/browser/sessions/session_backend_android.cc

+// Copyright (c) 2012 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/sessions/session_backend.h"
+
+#include "base/stl_util.h"
+#include "net/base/file_stream.h"
+
+// Dummy session backend for Android. Tab and session persistence is handled

[sky, 2012/09/26 20:54:21]

If tab and session persistence is handled else where, why is the sessions code
even compiled?

[Philippe, 2012/09/26 21:28:09]

That's a good question. We do use TabRestoreService::CreateHistoricalTab()
internally on the app side. Although we use here a dummy backend I suspect that
we rely on TabRestoreService's observers notification in some way which would be
the only no-op on Android (see NotifyTabsChanged() in
TabRestoreService::AddEntry()).
Unfortunately I'm not really familiar with this code. Do you  know who is
subscribing to these notifications and what would be the impact of not receiving
them?
I didn't see any Android-specific code subscribing to these notifications and
have really no idea why we do call TabRestoreService::CreateHistoricalTab(). You
might have an idea.
It's hard to track the file history internally on the app side with all the
merges and moves. 

[Philippe, 2012/09/26 21:38:10]

s/no-op/op. I meant notifications seem to be the only operation we do on Android
since we are using this dummy backend which doesn't do any actual read/write.

+// Java side.
+
+const int SessionBackend::kFileReadBufferSize = 0;
+
+SessionBackend::SessionBackend(BaseSessionService::SessionType type,
+                               const FilePath& path_to_dir)
+    : type_(type),
+      path_to_dir_(path_to_dir) {
+}
+
+void SessionBackend::Init() {
+}
+
+void SessionBackend::AppendCommands(std::vector<SessionCommand*>* commands,
+                                    bool reset_first) {
+  STLDeleteElements(commands);
+  delete commands;
+}
+
+void SessionBackend::ReadLastSessionCommands(
+    scoped_refptr<BaseSessionService::InternalGetCommandsRequest> request) {
+  if (request->canceled())
+    return;
+  Init();
+  ReadLastSessionCommandsImpl(&(request->commands));
+  request->ForwardResult(request->handle(), request);
+}
+
+bool SessionBackend::ReadLastSessionCommandsImpl(
+    std::vector<SessionCommand*>* commands) {
+  commands->clear();
+  return false;
+}
+
+void SessionBackend::DeleteLastSession() {
+}
+
+void SessionBackend::MoveCurrentSessionToLastSession() {
+}
+
+void SessionBackend::ReadCurrentSessionCommands(
+    scoped_refptr<BaseSessionService::InternalGetCommandsRequest> request) {
+  if (request->canceled())
+    return;
+  Init();
+  ReadCurrentSessionCommandsImpl(&(request->commands));
+  request->ForwardResult(request->handle(), request);
+}
+
+bool SessionBackend::ReadCurrentSessionCommandsImpl(
+    std::vector<SessionCommand*>* commands) {
+  commands->clear();
+  return false;
+}
+
+SessionBackend::~SessionBackend() {
+}