Introduce ChromeZoomLevelPref, make zoom level prefs independent of profile prefs.

chrome/browser/ui/zoom/chrome_zoom_level_prefs.cc

+// Copyright (c) 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.
+
+#include "chrome/browser/ui/zoom/chrome_zoom_level_prefs.h"
+
+#include <sstream>
+
+#include "base/bind.h"
+#include "base/prefs/json_pref_store.h"
+#include "base/prefs/pref_filter.h"
+#include "base/prefs/pref_registry_simple.h"
+#include "base/prefs/pref_service_factory.h"
+#include "base/prefs/scoped_user_pref_update.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/values.h"
+#include "chrome/common/chrome_constants.h"
+#include "chrome/common/pref_names.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/host_zoom_map.h"
+#include "content/public/common/page_zoom.h"
+
+namespace chrome {
+
+std::string ChromeZoomLevelPrefs::GetHash(const base::FilePath& relative_path) {
+  size_t int_key =
+#if defined(COMPILER_MSVC)
+      BASE_HASH_NAMESPACE::hash_value(relative_path);
+#else
+      BASE_HASH_NAMESPACE::hash<base::FilePath>()(relative_path);
+#endif  // COMPILER
+  return base::SizeTToString(int_key);
+}
+
+ChromeZoomLevelPrefs::ChromeZoomLevelPrefs(PrefService* pref_service,
+                                           const base::FilePath& profile_path)
+    : pref_service_(pref_service),
+      profile_path_(profile_path),
+      host_zoom_map_(nullptr) {
+  DCHECK(pref_service_);
+}
+
+ChromeZoomLevelPrefs::~ChromeZoomLevelPrefs() {
+}
+
+void ChromeZoomLevelPrefs::InitPrefsAndCopyToHostZoomMap(
+    const base::FilePath& partition_path,
+    content::HostZoomMap* host_zoom_map) {
+  DCHECK(!partition_path.empty());
+  DCHECK((partition_path == profile_path_) ||
+         profile_path_.IsParent(partition_path));
+  // This init function must be called only once.
+  DCHECK(!host_zoom_map_);
+  DCHECK(host_zoom_map);
+  host_zoom_map_ = host_zoom_map;
+
+  // Create a partition_key string with no '.'s in it. For the default
+  // StoragePartition, this string will always be "0".
+  base::FilePath partition_relative_path;
+  profile_path_.AppendRelativePath(partition_path, &partition_relative_path);
+  partition_key_ = GetHash(partition_relative_path);
+
+  // Initialize the default zoom level.
+  host_zoom_map_->SetDefaultZoomLevel(GetDefaultZoomLevelPref());
+
+  // Initialize the HostZoomMap with per-host zoom levels from the persisted
+  // zoom-level preference values.
+  const base::DictionaryValue* host_zoom_dictionaries =
+      pref_service_->GetDictionary(prefs::kPartitionPerHostZoomLevels);
+  const base::DictionaryValue* host_zoom_dictionary = nullptr;
+  if (host_zoom_dictionaries->GetDictionary(partition_key_,
+                                            &host_zoom_dictionary)) {
+    ExtractPerHostZoomLevels(host_zoom_dictionary);

[battre, 2014/10/10 15:41:08]

Here is a time dependency that should be documented in order to prevent
concurrent modifications while iterating over a dictionary:

ExtractPerHostZoomLevels takes the values from the dictionary and updates the
host_zoom_map_. If the subscription of line 75 were to be placed before line 71,
we would iterate over a dictionary that is indirectly modified by the
OnZoomLevelChanged handler.

[wjmaclean, 2014/10/10 17:14:10]

I've added a comment here, but the important change is iterating over a copy in
the extract function (see comment for line 158)

+  }
+  zoom_subscription_ = host_zoom_map_->AddZoomLevelChangedCallback(base::Bind(
+      &ChromeZoomLevelPrefs::OnZoomLevelChanged, base::Unretained(this)));
+}
+
+void ChromeZoomLevelPrefs::SetDefaultZoomLevelPref(double level) {
+  if (content::ZoomValuesEqual(level, host_zoom_map_->GetDefaultZoomLevel()))
+    return;
+
+  DictionaryPrefUpdate update(pref_service_, prefs::kPartitionDefaultZoomLevel);
+  update->SetDouble(partition_key_, level);
+  // For unregistered paths, OnDefaultZoomLevelChanged won't be called, so
+  // set this manually.
+  host_zoom_map_->SetDefaultZoomLevel(level);
+  default_zoom_changed_callbacks_.Notify();
+}
+
+double ChromeZoomLevelPrefs::GetDefaultZoomLevelPref() const {
+  double default_zoom_level = 0.0;
+
+  const base::DictionaryValue* default_zoom_level_dictionary =
+      pref_service_->GetDictionary(prefs::kPartitionDefaultZoomLevel);
+  // If no default has been previously set, the default returned is the
+  // value used to initialize default_zoom_level in this function.
+  default_zoom_level_dictionary->GetDouble(partition_key_, &default_zoom_level);
+  return default_zoom_level;
+}
+
+scoped_ptr<ChromeZoomLevelPrefs::DefaultZoomLevelSubscription>
+ChromeZoomLevelPrefs::RegisterDefaultZoomLevelCallback(
+    const base::Closure& callback) {
+  return default_zoom_changed_callbacks_.Add(callback);
+}
+
+void ChromeZoomLevelPrefs::OnZoomLevelChanged(
+    const content::HostZoomMap::ZoomLevelChange& change) {
+  if (change.mode != content::HostZoomMap::ZOOM_CHANGED_FOR_HOST)
+    return;
+  double level = change.zoom_level;
+  DictionaryPrefUpdate update(pref_service_,
+                              prefs::kPartitionPerHostZoomLevels);
+  base::DictionaryValue* host_zoom_dictionaries = update.Get();
+  DCHECK(host_zoom_dictionaries);
+
+  bool modification_is_removal =
+      content::ZoomValuesEqual(level, host_zoom_map_->GetDefaultZoomLevel());
+
+  base::DictionaryValue* host_zoom_dictionary = nullptr;
+  if (!host_zoom_dictionaries->GetDictionary(partition_key_,
+                                             &host_zoom_dictionary)) {
+    host_zoom_dictionary = new base::DictionaryValue();
+    host_zoom_dictionaries->Set(partition_key_, host_zoom_dictionary);
+  }
+
+  if (modification_is_removal)
+    host_zoom_dictionary->RemoveWithoutPathExpansion(change.host, nullptr);
+  else
+    host_zoom_dictionary->SetDoubleWithoutPathExpansion(change.host, level);
+}
+
+void ChromeZoomLevelPrefs::ExtractPerHostZoomLevels(
+    const base::DictionaryValue* host_zoom_dictionary) {
+  std::vector<std::string> keys_to_remove;
+  for (base::DictionaryValue::Iterator i(*host_zoom_dictionary); !i.IsAtEnd();
+       i.Advance()) {
+    const std::string& host(i.key());
+    double zoom_level = 0;
+
+    bool has_valid_zoom_level = i.value().GetAsDouble(&zoom_level);
+
+    // Filter out A) the empty host, B) zoom levels equal to the default; and
+    // remember them, so that we can later erase them from Prefs.
+    // Values of type A and B could have been stored due to crbug.com/364399.
+    // Values of type B could further have been stored before the default zoom
+    // level was set to its current value. In either case, SetZoomLevelForHost
+    // will ignore type B values, thus, to have consistency with HostZoomMap's
+    // internal state, these values must also be removed from Prefs.
+    if (host.empty() || !has_valid_zoom_level ||
+        content::ZoomValuesEqual(zoom_level,
+                                 host_zoom_map_->GetDefaultZoomLevel())) {
+      keys_to_remove.push_back(host);
+      continue;
+    }
+
+    host_zoom_map_->SetZoomLevelForHost(host, zoom_level);

[battre, 2014/10/10 15:41:08]

Note that this may modify the host_zoom_dictionary. Maybe we should create a
copy of host_zoom_dictionary before iterating over it.

[wjmaclean, 2014/10/10 17:14:10]

I think making a copy is the safest way to avoid the time dependency, since we
have no guarantee that this function isn't called after the HostZoomMap
subscription is setup on line 75.

Done.

+  }
+
+  // Sanitize prefs to remove entries that match the default zoom level and/or
+  // have an empty host.
+  {
+    DictionaryPrefUpdate update(pref_service_,
+                                prefs::kPartitionPerHostZoomLevels);
+    base::DictionaryValue* host_zoom_dictionaries = update.Get();
+    base::DictionaryValue* host_zoom_dictionary = nullptr;
+    host_zoom_dictionaries->GetDictionary(partition_key_,
+                                          &host_zoom_dictionary);
+    for (const std::string& s : keys_to_remove)
+      host_zoom_dictionary->RemoveWithoutPathExpansion(s, nullptr);
+  }
+}
+
+}  // namespace chrome