Add the SiteCharacteristicsDataStore class.

See the (@google.com) design doc: https://docs.google.com/document/d/1MgyIJ096pQChpbqQIqXHTZ0NYRXAOxcBtAq2lJplOpE/edit?usp=sharing

Bug: 773382
Change-Id: Ieff80131e2df38867c059047467abefdd9fe06a7
Reviewed-on: https://chromium-review.googlesource.com/1011253
Commit-Queue: Sébastien Marchand <sebmarchand@chromium.org>
Reviewed-by: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#552718}

chrome/browser/BUILD.gn

@@ -2617,8 +2617,11 @@ jumbo_split_static_library("browser") {
       "resource_coordinator/local_site_characteristics_data_impl.h",
       "resource_coordinator/local_site_characteristics_data_reader.cc",
       "resource_coordinator/local_site_characteristics_data_reader.h",
+      "resource_coordinator/local_site_characteristics_data_store.cc",
+      "resource_coordinator/local_site_characteristics_data_store.h",
       "resource_coordinator/local_site_characteristics_feature_usage.h",
       "resource_coordinator/site_characteristics_data_reader.h",
+      "resource_coordinator/site_characteristics_data_store.h",
       "resource_coordinator/tab_activity_watcher.cc",
       "resource_coordinator/tab_activity_watcher.h",
       "resource_coordinator/tab_lifecycle_observer.h",

chrome/browser/resource_coordinator/local_site_characteristics_data_impl.cc

@@ -39,17 +39,6 @@ const int64_t
         LocalSiteCharacteristicsDataImpl::TimeDeltaToInternalRepresentation(
             base::TimeDelta());
 
-LocalSiteCharacteristicsDataImpl::LocalSiteCharacteristicsDataImpl(
-    const std::string& origin_str)
-    : origin_str_(origin_str), active_webcontents_count_(0U) {
-  // Initialize the features element with the default value, this is required
-  // because some fields might otherwise never be initialized.
-  for (auto* iter : GetAllFeaturesFromProto(&site_characteristics_))
-    InitSiteCharacteristicsFeatureProtoWithDefaultValues(iter);
-
-  site_characteristics_.set_last_loaded(kZeroIntervalInternalRepresentation);
-}
-
 void LocalSiteCharacteristicsDataImpl::NotifySiteLoaded() {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   // Update the last loaded time when this origin gets loaded for the first
@@ -128,6 +117,21 @@ void LocalSiteCharacteristicsDataImpl::NotifyUsesNotificationsInBackground() {
       site_characteristics_.mutable_uses_notifications_in_background());
 }
 
+LocalSiteCharacteristicsDataImpl::LocalSiteCharacteristicsDataImpl(
+    const std::string& origin_str,
+    OnDestroyDelegate* delegate)
+    : origin_str_(origin_str),
+      active_webcontents_count_(0U),
+      delegate_(delegate) {
+  DCHECK_NE(nullptr, delegate_);
+  // Initialize the feature elements with the default value, this is required
+  // because some fields might otherwise never be initialized.
+  for (auto* iter : GetAllFeaturesFromProto(&site_characteristics_))
+    InitSiteCharacteristicsFeatureProtoWithDefaultValues(iter);
+
+  site_characteristics_.set_last_loaded(kZeroIntervalInternalRepresentation);
+}
+
 base::TimeDelta LocalSiteCharacteristicsDataImpl::FeatureObservationDuration(
     const SiteCharacteristicsFeatureProto& feature_proto) const {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
@@ -156,6 +160,9 @@ LocalSiteCharacteristicsDataImpl::~LocalSiteCharacteristicsDataImpl() {
   // object.
   // TODO(sebmarchand): Check if this is a valid assumption.
   DCHECK_EQ(0U, active_webcontents_count_);
+
+  DCHECK_NE(nullptr, delegate_);
+  delegate_->OnLocalSiteCharacteristicsDataImplDestroyed(this);
 }
 
 // static:

chrome/browser/resource_coordinator/local_site_characteristics_data_impl.h

@@ -15,23 +15,41 @@
 #include "chrome/browser/resource_coordinator/site_characteristics.pb.h"
 
 namespace resource_coordinator {
+
+class LocalSiteCharacteristicsDataStore;
+class LocalSiteCharacteristicsDataReaderTest;
+
 namespace internal {
 
-// Tracks observations for a given site. This class shouldn't be used
-// directly, it's meant to be used internally by the local site heuristic
-// database.
+// Internal class used to read/write site characteristics. This is a wrapper
+// class around a SiteCharacteristicsProto object and offers various to query
+// and/or modify it. This class shouldn't be used directly, instead it should be
+// created by a LocalSiteCharacteristicsDataStore that will serve reader and
+// writer objects.
+//
+// Reader and writers objects that are interested in reading/writing information
+// about the same origin will share a unique ref counted instance of this
+// object, because of this all the operations done on these objects should be
+// done on the same thread, this class isn't thread safe.
 class LocalSiteCharacteristicsDataImpl
     : public base::RefCounted<LocalSiteCharacteristicsDataImpl> {
  public:
-  explicit LocalSiteCharacteristicsDataImpl(const std::string& origin_str);
+  // Interface that should be implemented in order to receive notifications when
+  // this object is about to get destroyed.
+  class OnDestroyDelegate {
+   public:
+    // Called when this object is about to get destroyed.
+    virtual void OnLocalSiteCharacteristicsDataImplDestroyed(
+        LocalSiteCharacteristicsDataImpl* impl) = 0;
+  };
 
   // Must be called when a load event is received for this site, this can be
-  // invoked several time if instances of this class are shared between
+  // invoked several times if instances of this class are shared between
   // multiple tabs.
   void NotifySiteLoaded();
 
   // Must be called when an unload event is received for this site, this can be
-  // invoked several time if instances of this class are shared between
+  // invoked several times if instances of this class are shared between
   // multiple tabs.
   void NotifySiteUnloaded();
 
@@ -54,6 +72,11 @@ class LocalSiteCharacteristicsDataImpl
  protected:
   friend class base::RefCounted<LocalSiteCharacteristicsDataImpl>;
   friend class LocalSiteCharacteristicsDataImplTest;
+  friend class resource_coordinator::LocalSiteCharacteristicsDataReaderTest;
+  friend class resource_coordinator::LocalSiteCharacteristicsDataStore;
+
+  LocalSiteCharacteristicsDataImpl(const std::string& origin_str,
+                                   OnDestroyDelegate* delegate);
 
   // Helper functions to convert from/to the internal representation that is
   // used to store TimeDelta values in the |SiteCharacteristicsProto| protobuf.
@@ -67,6 +90,8 @@ class LocalSiteCharacteristicsDataImpl
 
   // Returns the minimum observation time before considering a feature as
   // unused.
+  // TODO(sebmarchand): Make these experimentally configurable, define the
+  // experiment variables in tab_manager_features.h.
   static constexpr base::TimeDelta
   GetUpdatesFaviconInBackgroundMinObservationWindow() {
     return base::TimeDelta::FromHours(2);
@@ -86,7 +111,7 @@ class LocalSiteCharacteristicsDataImpl
 
   virtual ~LocalSiteCharacteristicsDataImpl();
 
-  // Returns the observation duration for a given feature, this is the sum of
+  // Returns for how long a given feature has been observed, this is the sum of
   // the recorded observation duration and the current observation duration
   // since this site has been loaded (if applicable). If a feature has been
   // used then it returns 0.
@@ -103,6 +128,8 @@ class LocalSiteCharacteristicsDataImpl
     return site_characteristics_;
   }
 
+  const std::string& origin_str() const { return origin_str_; }
+
   static const int64_t kZeroIntervalInternalRepresentation;
 
  private:
@@ -139,6 +166,10 @@ class LocalSiteCharacteristicsDataImpl
   // tab gets loaded, stops when the last one gets unloaded).
   size_t active_webcontents_count_;
 
+  // The delegate that should get notified when this object is about to get
+  // destroyed.
+  OnDestroyDelegate* const delegate_;
+
   SEQUENCE_CHECKER(sequence_checker_);
   DISALLOW_COPY_AND_ASSIGN(LocalSiteCharacteristicsDataImpl);
 };

chrome/browser/resource_coordinator/local_site_characteristics_data_impl_unittest.cc

@@ -7,7 +7,9 @@
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/test/simple_test_tick_clock.h"
+#include "chrome/browser/resource_coordinator/local_site_characteristics_data_unittest_utils.h"
 #include "chrome/browser/resource_coordinator/time.h"
+#include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace resource_coordinator {
@@ -22,17 +24,20 @@ constexpr base::TimeDelta kInitialTimeSinceEpoch =
 class TestLocalSiteCharacteristicsDataImpl
     : public LocalSiteCharacteristicsDataImpl {
  public:
+  using LocalSiteCharacteristicsDataImpl::FeatureObservationDuration;
   using LocalSiteCharacteristicsDataImpl::
       GetUsesAudioInBackgroundMinObservationWindow;
   using LocalSiteCharacteristicsDataImpl::
       GetUsesNotificationsInBackgroundMinObservationWindow;
-  using LocalSiteCharacteristicsDataImpl::FeatureObservationDuration;
+  using LocalSiteCharacteristicsDataImpl::last_loaded_time_for_testing;
+  using LocalSiteCharacteristicsDataImpl::OnDestroyDelegate;
   using LocalSiteCharacteristicsDataImpl::site_characteristics_for_testing;
   using LocalSiteCharacteristicsDataImpl::TimeDeltaToInternalRepresentation;
-  using LocalSiteCharacteristicsDataImpl::last_loaded_time_for_testing;
 
-  explicit TestLocalSiteCharacteristicsDataImpl(const std::string& origin_str)
-      : LocalSiteCharacteristicsDataImpl(origin_str) {}
+  explicit TestLocalSiteCharacteristicsDataImpl(
+      const std::string& origin_str,
+      LocalSiteCharacteristicsDataImpl::OnDestroyDelegate* delegate)
+      : LocalSiteCharacteristicsDataImpl(origin_str, delegate) {}
 
   base::TimeDelta FeatureObservationTimestamp(
       const SiteCharacteristicsFeatureProto& feature_proto) {
@@ -40,12 +45,12 @@ class TestLocalSiteCharacteristicsDataImpl
   }
 
  protected:
-  ~TestLocalSiteCharacteristicsDataImpl() override{};
+  ~TestLocalSiteCharacteristicsDataImpl() override {}
 };
 
 }  // namespace
 
-class LocalSiteCharacteristicsDataImplTest : public testing::Test {
+class LocalSiteCharacteristicsDataImplTest : public ::testing::Test {
  public:
   LocalSiteCharacteristicsDataImplTest()
       : scoped_set_tick_clock_for_testing_(&test_clock_) {}
@@ -60,11 +65,17 @@ class LocalSiteCharacteristicsDataImplTest : public testing::Test {
  protected:
   base::SimpleTestTickClock test_clock_;
   ScopedSetTickClockForTesting scoped_set_tick_clock_for_testing_;
+  // Use a NiceMock as there's no need to add expectations in these tests,
+  // there's a dedicated test that ensure that the delegate works as expected.
+  ::testing::NiceMock<
+      testing::MockLocalSiteCharacteristicsDataImplOnDestroyDelegate>
+      destroy_delegate_;
 };
 
 TEST_F(LocalSiteCharacteristicsDataImplTest, BasicTestEndToEnd) {
   auto local_site_data =
-      base::MakeRefCounted<TestLocalSiteCharacteristicsDataImpl>(kDummyOrigin);
+      base::MakeRefCounted<TestLocalSiteCharacteristicsDataImpl>(
+          kDummyOrigin, &destroy_delegate_);
 
   local_site_data->NotifySiteLoaded();
 
@@ -120,7 +131,8 @@ TEST_F(LocalSiteCharacteristicsDataImplTest, BasicTestEndToEnd) {
 
 TEST_F(LocalSiteCharacteristicsDataImplTest, LastLoadedTime) {
   auto local_site_data =
-      base::MakeRefCounted<TestLocalSiteCharacteristicsDataImpl>(kDummyOrigin);
+      base::MakeRefCounted<TestLocalSiteCharacteristicsDataImpl>(
+          kDummyOrigin, &destroy_delegate_);
   // Create a second instance of this object, simulates having several tab
   // owning it.
   auto local_site_data2(local_site_data);
@@ -150,7 +162,8 @@ TEST_F(LocalSiteCharacteristicsDataImplTest, LastLoadedTime) {
 
 TEST_F(LocalSiteCharacteristicsDataImplTest, GetFeatureUsageForUnloadedSite) {
   auto local_site_data =
-      base::MakeRefCounted<TestLocalSiteCharacteristicsDataImpl>(kDummyOrigin);
+      base::MakeRefCounted<TestLocalSiteCharacteristicsDataImpl>(
+          kDummyOrigin, &destroy_delegate_);
 
   local_site_data->NotifySiteLoaded();
   local_site_data->NotifyUsesAudioInBackground();
@@ -203,7 +216,8 @@ TEST_F(LocalSiteCharacteristicsDataImplTest, AllDurationGetSavedOnUnload) {
   // This test helps making sure that the observation/timestamp fields get saved
   // for all the features being tracked.
   auto local_site_data =
-      base::MakeRefCounted<TestLocalSiteCharacteristicsDataImpl>(kDummyOrigin);
+      base::MakeRefCounted<TestLocalSiteCharacteristicsDataImpl>(
+          kDummyOrigin, &destroy_delegate_);
 
   const base::TimeDelta kInterval = base::TimeDelta::FromSeconds(1);
   const auto kIntervalInternalRepresentation =
@@ -266,5 +280,21 @@ TEST_F(LocalSiteCharacteristicsDataImplTest, AllDurationGetSavedOnUnload) {
       local_site_data->site_characteristics_for_testing().SerializeAsString());
 }
 
+// Verify that the OnDestroyDelegate gets notified when a
+// LocalSiteCharacteristicsDataImpl object gets destroyed.
+TEST_F(LocalSiteCharacteristicsDataImplTest, DestroyNotifiesDelegate) {
+  ::testing::StrictMock<
+      testing::MockLocalSiteCharacteristicsDataImplOnDestroyDelegate>
+      strict_delegate;
+  {
+    auto local_site_data =
+        base::MakeRefCounted<TestLocalSiteCharacteristicsDataImpl>(
+            kDummyOrigin, &strict_delegate);
+    EXPECT_CALL(strict_delegate, OnLocalSiteCharacteristicsDataImplDestroyed(
+                                     local_site_data.get()));
+  }
+  ::testing::Mock::VerifyAndClear(&strict_delegate);
+}
+
 }  // namespace internal
 }  // namespace resource_coordinator

chrome/browser/resource_coordinator/local_site_characteristics_data_reader.h

@@ -30,11 +30,11 @@ class LocalSiteCharacteristicsDataReader
 
  private:
   friend class LocalSiteCharacteristicsDataReaderTest;
+  friend class LocalSiteCharacteristicsDataStoreTest;
+  friend class LocalSiteCharacteristicsDataStore;
 
   // Private constructor, these objects are meant to be created by a site
-  // characteristics data store (not currently implemented).
-  // TODO(sebmarchand): Update this comment once the site characteristics data
-  // store class gets implemented.
+  // characteristics data store.
   explicit LocalSiteCharacteristicsDataReader(
       scoped_refptr<internal::LocalSiteCharacteristicsDataImpl> impl);
 

chrome/browser/resource_coordinator/local_site_characteristics_data_reader_unittest.cc

@@ -8,18 +8,23 @@
 #include "base/memory/ptr_util.h"
 #include "base/test/simple_test_tick_clock.h"
 #include "chrome/browser/resource_coordinator/local_site_characteristics_data_impl.h"
+#include "chrome/browser/resource_coordinator/local_site_characteristics_data_unittest_utils.h"
 #include "chrome/browser/resource_coordinator/time.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace resource_coordinator {
 
-class LocalSiteCharacteristicsDataReaderTest : public testing::Test {
- public:
+class LocalSiteCharacteristicsDataReaderTest : public ::testing::Test {
+ protected:
+  // The constructors needs to call 'new' directly rather than using the
+  // base::MakeRefCounted helper function because the constructor of
+  // LocalSiteCharacteristicsDataImpl is protected and not visible to
+  // base::MakeRefCounted.
   LocalSiteCharacteristicsDataReaderTest()
       : scoped_set_tick_clock_for_testing_(&test_clock_),
-        test_impl_(
-            base::MakeRefCounted<internal::LocalSiteCharacteristicsDataImpl>(
-                "foo.com")) {
+        test_impl_(base::WrapRefCounted(
+            new internal::LocalSiteCharacteristicsDataImpl("foo.com",
+                                                           &delegate_))) {
     test_impl_->NotifySiteLoaded();
     LocalSiteCharacteristicsDataReader* reader =
         new LocalSiteCharacteristicsDataReader(test_impl_.get());
@@ -28,9 +33,10 @@ class LocalSiteCharacteristicsDataReaderTest : public testing::Test {
 
   ~LocalSiteCharacteristicsDataReaderTest() override {
     test_impl_->NotifySiteUnloaded();
+    reader_.reset();
+    test_impl_ = nullptr;
   }
 
- protected:
   base::SimpleTestTickClock test_clock_;
   ScopedSetTickClockForTesting scoped_set_tick_clock_for_testing_;
 
@@ -41,6 +47,13 @@ class LocalSiteCharacteristicsDataReaderTest : public testing::Test {
   // to create this object.
   std::unique_ptr<LocalSiteCharacteristicsDataReader> reader_;
 
+  // The mock delegate used by the LocalSiteCharacteristicsDataImpl objects
+  // created by this class, NiceMock is used to avoid having to set expectations
+  // in test cases that don't care about this.
+  ::testing::NiceMock<
+      testing::MockLocalSiteCharacteristicsDataImplOnDestroyDelegate>
+      delegate_;
+
   DISALLOW_COPY_AND_ASSIGN(LocalSiteCharacteristicsDataReaderTest);
 };
 

chrome/browser/resource_coordinator/local_site_characteristics_data_store.cc

+// Copyright 2018 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/resource_coordinator/local_site_characteristics_data_store.h"
+
+#include "base/memory/ptr_util.h"
+#include "base/stl_util.h"
+#include "chrome/browser/resource_coordinator/local_site_characteristics_data_reader.h"
+
+namespace resource_coordinator {
+
+LocalSiteCharacteristicsDataStore::LocalSiteCharacteristicsDataStore() =
+    default;
+
+LocalSiteCharacteristicsDataStore::~LocalSiteCharacteristicsDataStore() =
+    default;
+
+std::unique_ptr<SiteCharacteristicsDataReader>
+LocalSiteCharacteristicsDataStore::GetReaderForOrigin(
+    const std::string& origin_str) {
+  internal::LocalSiteCharacteristicsDataImpl* impl =
+      GetOrCreateFeatureImpl(origin_str);
+  DCHECK_NE(nullptr, impl);
+  SiteCharacteristicsDataReader* data_reader =
+      new LocalSiteCharacteristicsDataReader(impl);
+  return base::WrapUnique(data_reader);
+}
+
+internal::LocalSiteCharacteristicsDataImpl*
+LocalSiteCharacteristicsDataStore::GetOrCreateFeatureImpl(
+    const std::string& origin_str) {
+  // Start by checking if there's already an entry for this origin.
+  auto iter = origin_data_map_.find(origin_str);
+  if (iter != origin_data_map_.end())
+    return iter->second;
+
+  // If not create a new one and add it to the map.
+  internal::LocalSiteCharacteristicsDataImpl* site_characteristic_data =
+      new internal::LocalSiteCharacteristicsDataImpl(origin_str, this);
+  // internal::LocalSiteCharacteristicsDataImpl is a ref-counted object, it's
+  // safe to store a raw pointer to it here as this class will get notified when
+  // it's about to be destroyed and it'll be removed from the map.
+  origin_data_map_.insert(std::make_pair(origin_str, site_characteristic_data));
+  return site_characteristic_data;
+}
+
+void LocalSiteCharacteristicsDataStore::
+    OnLocalSiteCharacteristicsDataImplDestroyed(
+        internal::LocalSiteCharacteristicsDataImpl* impl) {
+  DCHECK_NE(nullptr, impl);
+  DCHECK(base::ContainsKey(origin_data_map_, impl->origin_str()));
+  // Remove the entry for this origin as this is about to get destroyed.
+  auto num_erased = origin_data_map_.erase(impl->origin_str());
+  DCHECK_EQ(1U, num_erased);
+}
+
+}  // namespace resource_coordinator

chrome/browser/resource_coordinator/local_site_characteristics_data_store.h

+// Copyright 2018 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 CHROME_BROWSER_RESOURCE_COORDINATOR_LOCAL_SITE_CHARACTERISTICS_DATA_STORE_H_
+#define CHROME_BROWSER_RESOURCE_COORDINATOR_LOCAL_SITE_CHARACTERISTICS_DATA_STORE_H_
+
+#include "base/containers/flat_map.h"
+#include "base/macros.h"
+#include "chrome/browser/resource_coordinator/local_site_characteristics_data_impl.h"
+#include "chrome/browser/resource_coordinator/site_characteristics_data_store.h"
+
+namespace resource_coordinator {
+
+// Implementation of a SiteCharacteristicsDataStore that use the local site
+// characteristics database as a backend.
+class LocalSiteCharacteristicsDataStore
+    : public SiteCharacteristicsDataStore,
+      public internal::LocalSiteCharacteristicsDataImpl::OnDestroyDelegate {
+ public:
+  using LocalSiteCharacteristicsMap =
+      base::flat_map<std::string, internal::LocalSiteCharacteristicsDataImpl*>;
+
+  LocalSiteCharacteristicsDataStore();
+  ~LocalSiteCharacteristicsDataStore() override;
+
+  // SiteCharacteristicDataStore:
+  std::unique_ptr<SiteCharacteristicsDataReader> GetReaderForOrigin(
+      const std::string& origin_str) override;
+
+  const LocalSiteCharacteristicsMap& origin_data_map_for_testing() const {
+    return origin_data_map_;
+  }
+
+ private:
+  // Returns a pointer to the LocalSiteCharacteristicsDataImpl object
+  // associated with |origin|, create one and add it to |origin_data_map_|
+  // if it doesn't exist.
+  internal::LocalSiteCharacteristicsDataImpl* GetOrCreateFeatureImpl(
+      const std::string& origin_str);
+
+  // internal::LocalSiteCharacteristicsDataImpl::OnDestroyDelegate:
+  void OnLocalSiteCharacteristicsDataImplDestroyed(
+      internal::LocalSiteCharacteristicsDataImpl* impl) override;
+
+  // Map a serialized origin to a LocalSiteCharacteristicDataInternal
+  // pointer.
+  LocalSiteCharacteristicsMap origin_data_map_;
+
+  DISALLOW_COPY_AND_ASSIGN(LocalSiteCharacteristicsDataStore);
+};
+
+}  // namespace resource_coordinator
+
+#endif  // CHROME_BROWSER_RESOURCE_COORDINATOR_LOCAL_SITE_CHARACTERISTICS_DATA_STORE_H_

chrome/browser/resource_coordinator/local_site_characteristics_data_store_unittest.cc

+// Copyright 2018 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/resource_coordinator/local_site_characteristics_data_store.h"
+
+#include "base/macros.h"
+#include "chrome/browser/resource_coordinator/local_site_characteristics_data_impl.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace resource_coordinator {
+
+using LocalSiteCharacteristicsDataStoreTest = testing::Test;
+
+TEST_F(LocalSiteCharacteristicsDataStoreTest, EndToEnd) {
+  const std::string kOrigin = "foo.com";
+  LocalSiteCharacteristicsDataStore data_store;
+  EXPECT_TRUE(data_store.origin_data_map_for_testing().empty());
+  auto reader = data_store.GetReaderForOrigin(kOrigin);
+  EXPECT_NE(nullptr, reader.get());
+  EXPECT_EQ(1U, data_store.origin_data_map_for_testing().size());
+
+  internal::LocalSiteCharacteristicsDataImpl* impl =
+      data_store.origin_data_map_for_testing().find(kOrigin)->second;
+  EXPECT_NE(nullptr, impl);
+
+  EXPECT_EQ(SiteFeatureUsage::kSiteFeatureUsageUnknown,
+            reader->UpdatesTitleInBackground());
+  impl->NotifySiteLoaded();
+  impl->NotifyUpdatesTitleInBackground();
+  impl->NotifySiteUnloaded();
+  EXPECT_EQ(SiteFeatureUsage::kSiteFeatureInUse,
+            reader->UpdatesTitleInBackground());
+
+  auto reader_copy = data_store.GetReaderForOrigin(kOrigin);
+  EXPECT_EQ(1U, data_store.origin_data_map_for_testing().size());
+  reader_copy.reset();
+
+  reader.reset();
+  EXPECT_TRUE(data_store.origin_data_map_for_testing().empty());
+}
+
+}  // namespace resource_coordinator

chrome/browser/resource_coordinator/local_site_characteristics_data_unittest_utils.cc

+// Copyright 2018 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/resource_coordinator/local_site_characteristics_data_unittest_utils.h"
+
+namespace resource_coordinator {
+namespace testing {
+
+MockLocalSiteCharacteristicsDataImplOnDestroyDelegate::
+    MockLocalSiteCharacteristicsDataImplOnDestroyDelegate() = default;
+MockLocalSiteCharacteristicsDataImplOnDestroyDelegate::
+    ~MockLocalSiteCharacteristicsDataImplOnDestroyDelegate() = default;
+
+}  // namespace testing
+}  // namespace resource_coordinator

chrome/browser/resource_coordinator/local_site_characteristics_data_unittest_utils.h

+// Copyright 2018 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 CHROME_BROWSER_RESOURCE_COORDINATOR_LOCAL_SITE_CHARACTERISTICS_DATA_UNITTEST_UTILS_H_
+#define CHROME_BROWSER_RESOURCE_COORDINATOR_LOCAL_SITE_CHARACTERISTICS_DATA_UNITTEST_UTILS_H_
+
+#include "base/macros.h"
+#include "chrome/browser/resource_coordinator/local_site_characteristics_data_impl.h"
+#include "testing/gmock/include/gmock/gmock.h"
+
+namespace resource_coordinator {
+namespace testing {
+
+class MockLocalSiteCharacteristicsDataImplOnDestroyDelegate
+    : public internal::LocalSiteCharacteristicsDataImpl::OnDestroyDelegate {
+ public:
+  MockLocalSiteCharacteristicsDataImplOnDestroyDelegate();
+  ~MockLocalSiteCharacteristicsDataImplOnDestroyDelegate();
+
+  MOCK_METHOD1(OnLocalSiteCharacteristicsDataImplDestroyed,
+               void(internal::LocalSiteCharacteristicsDataImpl*));
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(
+      MockLocalSiteCharacteristicsDataImplOnDestroyDelegate);
+};
+
+}  // namespace testing
+}  // namespace resource_coordinator
+
+#endif  // CHROME_BROWSER_RESOURCE_COORDINATOR_LOCAL_SITE_CHARACTERISTICS_DATA_UNITTEST_UTILS_H_

chrome/browser/resource_coordinator/site_characteristics_data_store.h

+// Copyright 2018 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 CHROME_BROWSER_RESOURCE_COORDINATOR_SITE_CHARACTERISTICS_DATA_STORE_H_
+#define CHROME_BROWSER_RESOURCE_COORDINATOR_SITE_CHARACTERISTICS_DATA_STORE_H_
+
+#include <memory>
+#include <string>
+
+#include "base/macros.h"
+#include "chrome/browser/resource_coordinator/site_characteristics_data_reader.h"
+
+namespace resource_coordinator {
+
+// Pure virtual interface for a site characteristics data store.
+class SiteCharacteristicsDataStore {
+ public:
+  SiteCharacteristicsDataStore() = default;
+  virtual ~SiteCharacteristicsDataStore() {}
+
+  // Returns a SiteCharacteristicsDataReader for the given origin.
+  virtual std::unique_ptr<SiteCharacteristicsDataReader> GetReaderForOrigin(
+      const std::string& origin) = 0;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(SiteCharacteristicsDataStore);
+};
+
+}  // namespace resource_coordinator
+
+#endif  // CHROME_BROWSER_RESOURCE_COORDINATOR_SITE_CHARACTERISTICS_DATA_STORE_H_

chrome/test/BUILD.gn

@@ -2914,6 +2914,9 @@ test("unit_tests") {
       "../browser/resource_coordinator/lifecycle_unit_unittest.cc",
       "../browser/resource_coordinator/local_site_characteristics_data_impl_unittest.cc",
       "../browser/resource_coordinator/local_site_characteristics_data_reader_unittest.cc",
+      "../browser/resource_coordinator/local_site_characteristics_data_store_unittest.cc",
+      "../browser/resource_coordinator/local_site_characteristics_data_unittest_utils.cc",
+      "../browser/resource_coordinator/local_site_characteristics_data_unittest_utils.h",
       "../browser/resource_coordinator/tab_activity_watcher_unittest.cc",
       "../browser/resource_coordinator/tab_lifecycle_unit_source_unittest.cc",
       "../browser/resource_coordinator/tab_lifecycle_unit_unittest.cc",