Add Data Saver support to Cronet

components/cronet/android/cronet_pref_store.h

-// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// 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 ANDROID_WEBVIEW_BROWSER_AW_PREF_STORE_H_
-#define ANDROID_WEBVIEW_BROWSER_AW_PREF_STORE_H_
+#ifndef COMPONENTS_CRONET_ANDROID_CRONET_PREF_STORE_H_
+#define COMPONENTS_CRONET_ANDROID_CRONET_PREF_STORE_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/observer_list.h"
 #include "base/prefs/persistent_pref_store.h"
 #include "base/prefs/pref_value_map.h"
 
 // A light-weight prefstore implementation that keeps preferences
 // in a memory backed store. This is not a persistent prefstore -- we
 // subclass the PersistentPrefStore here since it is needed by the
 // PrefService, which in turn is needed by the Autofill component.

[mmenke, 2015/04/01 15:46:14]

As Helen said, the second sentence really makes no sense here.

[bengr, 2015/04/24 02:30:43]

Done.

-class AwPrefStore : public PersistentPrefStore {
+// TODO(bengr): Move to base/prefs or some other shared location.
+class CronetPrefStore : public PersistentPrefStore {

[mmenke, 2015/04/01 15:46:14]

Ok, so now I'm following why you needs a PersistentPrefStore - the main user
prefs use PrefService instead of PrefStore.

In Chrome, the network stack is using a PrefStore that lives on the IO thread to
store some network information, and I expect we'll add stuff to it over time. 
Wonder if it's worth considering using that for the DRP - may make life easier
if you can move more stuff over to the IO thread.  One down side is we load the
network prefs asynchronously, so we don't block startup on reading them.

Anyhow, beyond the scoped of this CL, but may be worth considering.

Alternatively, could just make the PrefService and StatisticsPrefs optional.  I
don't think we need either of them for Cronet, and they aren't really needed for
the DRP.

[mmenke, 2015/04/01 15:46:14]

We're actually going to be needing to use an on-disk pref store for SDCH in
Cronet, so this name is a bit misleading.  "CronetInMemoryPrefStore"?

[bengr, 2015/04/24 02:30:42]

Done.

[bengr, 2015/04/24 02:30:43]

Ack. Out of scope for this CL.

  public:
-  AwPrefStore();
+  CronetPrefStore();
 
-  // Overriden from PrefStore.
+  // Overrides from PrefStore:
   bool GetValue(const std::string& key,
                 const base::Value** result) const override;
   void AddObserver(PrefStore::Observer* observer) override;
   void RemoveObserver(PrefStore::Observer* observer) override;
   bool HasObservers() const override;
   bool IsInitializationComplete() const override;
 
   // PersistentPrefStore overrides:
-  bool GetMutableValue(const std::string& key, base::Value** result) override;
+  bool GetMutableValue(const std::string& key,
+                       base::Value** result) override;

[mmenke, 2015/04/01 15:46:14]

Can this all fit on a single line?  Looks like it did for the class you copied
from.

[bengr, 2015/04/24 02:30:43]

Done.

   void ReportValueChanged(const std::string& key) override;
   void SetValue(const std::string& key, base::Value* value) override;
-  void SetValueSilently(const std::string& key, base::Value* value) override;
+  void SetValueSilently(const std::string& key,
+                                base::Value* value) override;

[mmenke, 2015/04/01 15:46:14]

nit:  fix indent, or can this all fir on a single line?

[bengr, 2015/04/24 02:30:42]

Done.

   void RemoveValue(const std::string& key) override;
   bool ReadOnly() const override;
   PrefReadError GetReadError() const override;
   PersistentPrefStore::PrefReadError ReadPrefs() override;
   void ReadPrefsAsync(ReadErrorDelegate* error_delegate) override;
   void CommitPendingWrite() override {}
 
  protected:
-  ~AwPrefStore() override;
+  ~CronetPrefStore() override;

[mmenke, 2015/04/01 15:46:14]

Suggest making this private - no one should be inheriting from this.

[bengr, 2015/04/24 02:30:42]

Done.

 
  private:
   // Stores the preference values.
   PrefValueMap prefs_;
 
   ObserverList<PrefStore::Observer, true> observers_;
 
-  DISALLOW_COPY_AND_ASSIGN(AwPrefStore);
+  DISALLOW_COPY_AND_ASSIGN(CronetPrefStore);
 };
 
-#endif  // ANDROID_WEBVIEW_BROWSER_AW_PREF_STORE_H_
+#endif  // COMPONENTS_CRONET_ANDROID_CRONET_PREF_STORE_H_