Fixes and simplification to ShortcutsBackend including addition of "DeleteAll"

TEST=unit-tests
BUG=none
Review URL: http://codereview.chromium.org/7821011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@101611 0039d316-1c4b-4281-b951-d872f2087c98

9 files changed, 326 insertions, 321 deletions

diff --git a/chrome/browser/autocomplete/shortcuts_provider.cc b/chrome/browser/autocomplete/shortcuts_provider.cc
index 1b29dac..4ef6ae9 100644
--- a/chrome/browser/autocomplete/shortcuts_provider.cc
+++ b/chrome/browser/autocomplete/shortcuts_provider.cc
@@ -61,11 +61,12 @@ ShortcutsProvider::ShortcutsProvider(ACProviderListener* listener,
                                      Profile* profile)
     : AutocompleteProvider(listener, profile, "ShortcutsProvider"),
       languages_(profile_->GetPrefs()->GetString(prefs::kAcceptLanguages)),
+      initialized_(false),
       shortcuts_backend_(profile->GetShortcutsBackend()) {
   if (shortcuts_backend_.get()) {
     shortcuts_backend_->AddObserver(this);
     if (shortcuts_backend_->initialized())
-      LoadShortcuts();
+      initialized_ = true;
   }
 }
 
@@ -81,6 +82,9 @@ void ShortcutsProvider::Start(const AutocompleteInput& input,
   if (input.type() == AutocompleteInput::INVALID)
     return;
 
+  if (!initialized_)
+    return;
+
   base::TimeTicks start_time = base::TimeTicks::Now();
   GetMatches(input);
   if (input.text().length() < 6) {
@@ -114,29 +118,7 @@ void ShortcutsProvider::DeleteMatch(const AutocompleteMatch& match) {
 }
 
 void ShortcutsProvider::OnShortcutsLoaded() {
-  LoadShortcuts();
-}
-
-void ShortcutsProvider::OnShortcutAddedOrUpdated(const Shortcut& shortcut) {
-  shortcuts_provider::GuidToShortcutsIteratorMap::iterator it =
-      guid_map_.find(shortcut.id);
-  if (it != guid_map_.end()) {
-    shortcuts_map_.erase(it->second);
-  }
-  guid_map_[shortcut.id] = shortcuts_map_.insert(
-      std::make_pair(base::i18n::ToLower(shortcut.text), shortcut));
-}
-
-void ShortcutsProvider::OnShortcutsRemoved(
-    const std::vector<std::string>& shortcuts_ids) {
-  for (size_t i = 0; i < shortcuts_ids.size(); ++i) {
-    shortcuts_provider::GuidToShortcutsIteratorMap::iterator it =
-        guid_map_.find(shortcuts_ids[i]);
-    if (it != guid_map_.end()) {
-      shortcuts_map_.erase(it->second);
-      guid_map_.erase(it);
-    }
-  }
+  initialized_ = true;
 }
 
 void ShortcutsProvider::DeleteMatchesWithURLs(const std::set<GURL>& urls) {
@@ -145,13 +127,6 @@ void ShortcutsProvider::DeleteMatchesWithURLs(const std::set<GURL>& urls) {
 }
 
 void ShortcutsProvider::DeleteShortcutsWithURLs(const std::set<GURL>& urls) {
-  for (ShortcutMap::iterator it = shortcuts_map_.begin();
-       it != shortcuts_map_.end();) {
-    if (urls.find(it->second.url) != urls.end())
-      shortcuts_map_.erase(it++);
-    else
-      ++it;
-  }
   if (!shortcuts_backend_.get())
     return;  // We are off the record.
   for (std::set<GURL>::const_iterator url = urls.begin(); url != urls.end();
@@ -165,8 +140,8 @@ void ShortcutsProvider::GetMatches(const AutocompleteInput& input) {
   string16 term_string(base::i18n::ToLower(input.text()));
   DCHECK(!term_string.empty());
 
-  for (ShortcutMap::iterator it = FindFirstMatch(term_string);
-       it != shortcuts_map_.end() &&
+  for (ShortcutMap::const_iterator it = FindFirstMatch(term_string);
+       it != shortcuts_backend_->shortcuts_map().end() &&
             StartsWith(it->first, term_string, true); ++it)
     matches_.push_back(ShortcutToACMatch(input, term_string, it));
   std::partial_sort(matches_.begin(),
@@ -182,7 +157,7 @@ void ShortcutsProvider::GetMatches(const AutocompleteInput& input) {
 AutocompleteMatch ShortcutsProvider::ShortcutToACMatch(
     const AutocompleteInput& input,
     const string16& term_string,
-    ShortcutMap::iterator it) {
+    ShortcutMap::const_iterator it) {
   AutocompleteMatch match(this, CalculateScore(term_string, it->second),
                           true, AutocompleteMatch::HISTORY_TITLE);
   match.destination_url = it->second.url;
@@ -280,13 +255,15 @@ ACMatchClassifications ShortcutsProvider::ClassifyAllMatchesInString(
   return output;
 }
 
-ShortcutMap::iterator ShortcutsProvider::FindFirstMatch(
+ShortcutMap::const_iterator ShortcutsProvider::FindFirstMatch(
     const string16& keyword) {
-  ShortcutMap::iterator it = shortcuts_map_.lower_bound(keyword);
+  ShortcutMap::const_iterator it =
+      shortcuts_backend_->shortcuts_map().lower_bound(keyword);
   // Lower bound not necessarily matches the keyword, check for item pointed by
   // the lower bound iterator to at least start with keyword.
-  return ((it == shortcuts_map_.end()) ||
-    StartsWith(it->first, keyword, true)) ? it : shortcuts_map_.end();
+  return ((it == shortcuts_backend_->shortcuts_map().end()) ||
+    StartsWith(it->first, keyword, true)) ? it :
+    shortcuts_backend_->shortcuts_map().end();
 }
 
 // static
@@ -320,11 +297,11 @@ int ShortcutsProvider::CalculateScore(const string16& terms,
       0.5);
 }
 
-void ShortcutsProvider::LoadShortcuts() {
-  DCHECK(shortcuts_backend_.get());
-  guid_map_.clear();
-  CHECK(shortcuts_backend_->GetShortcuts(&shortcuts_map_));
-  for (shortcuts_provider::ShortcutMap::iterator it = shortcuts_map_.begin();
-       it != shortcuts_map_.end(); ++it)
-    guid_map_[it->second.id] = it;
+void ShortcutsProvider::set_shortcuts_backend(
+    history::ShortcutsBackend* shortcuts_backend) {
+  DCHECK(shortcuts_backend);
+  shortcuts_backend_ = shortcuts_backend;
+  shortcuts_backend_->AddObserver(this);
+  if (shortcuts_backend_->initialized())
+    initialized_ = true;
 }
diff --git a/chrome/browser/autocomplete/shortcuts_provider.h b/chrome/browser/autocomplete/shortcuts_provider.h
index 38161d4..d41a70b 100644
--- a/chrome/browser/autocomplete/shortcuts_provider.h
+++ b/chrome/browser/autocomplete/shortcuts_provider.h
@@ -51,10 +51,6 @@ class ShortcutsProvider
 
   // ShortcutsBackendObserver:
   virtual void OnShortcutsLoaded() OVERRIDE;
-  virtual void OnShortcutAddedOrUpdated(
-      const shortcuts_provider::Shortcut& shortcut) OVERRIDE;
-  virtual void OnShortcutsRemoved(
-      const std::vector<std::string>& shortcut_ids) OVERRIDE;
 
   void DeleteMatchesWithURLs(const std::set<GURL>& urls);
   void DeleteShortcutsWithURLs(const std::set<GURL>& urls);
@@ -65,7 +61,7 @@ class ShortcutsProvider
   AutocompleteMatch ShortcutToACMatch(
       const AutocompleteInput& input,
       const string16& terms,
-      shortcuts_provider::ShortcutMap::iterator it);
+      shortcuts_provider::ShortcutMap::const_iterator it);
 
   // Given |text| and a corresponding base set of classifications
   // |original_class|, adds ACMatchClassification::MATCH markers for all
@@ -85,25 +81,16 @@ class ShortcutsProvider
 
   // Returns iterator to first item in |shortcuts_map_| matching |keyword|.
   // Returns shortcuts_map_.end() if there are no matches.
-  shortcuts_provider::ShortcutMap::iterator FindFirstMatch(
+  shortcuts_provider::ShortcutMap::const_iterator FindFirstMatch(
       const string16& keyword);
 
   static int CalculateScore(const string16& terms,
                             const shortcuts_provider::Shortcut& shortcut);
-
-  // Loads shortcuts from the backend.
-  void LoadShortcuts();
+  // For unit-test only.
+  void set_shortcuts_backend(history::ShortcutsBackend* shortcuts_backend);
 
   std::string languages_;
-
-  // The following two maps are duplicated from the ShortcutsBackend. If any
-  // of the copies of ShortcutProvider makes a change and calls ShortcutBackend
-  // the change will be committed to storage and to the back-end's copy on the
-  // DB thread and propagated back to all copies of provider, so eventually they
-  // all are going to be in sync.
-  shortcuts_provider::ShortcutMap shortcuts_map_;
-  // This is a helper map for quick access to a shortcut by guid.
-  shortcuts_provider::GuidToShortcutsIteratorMap guid_map_;
+  bool initialized_;
 
   scoped_refptr<history::ShortcutsBackend> shortcuts_backend_;
 };
diff --git a/chrome/browser/autocomplete/shortcuts_provider_unittest.cc b/chrome/browser/autocomplete/shortcuts_provider_unittest.cc
index 534c53d..7b98206 100644
--- a/chrome/browser/autocomplete/shortcuts_provider_unittest.cc
+++ b/chrome/browser/autocomplete/shortcuts_provider_unittest.cc
@@ -18,6 +18,7 @@
 #include "chrome/browser/autocomplete/autocomplete_match.h"
 #include "chrome/browser/history/history.h"
 #include "chrome/browser/history/in_memory_url_index.h"
+#include "chrome/browser/history/shortcuts_backend.h"
 #include "chrome/browser/history/url_database.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/common/pref_names.h"
@@ -31,6 +32,7 @@ using base::TimeDelta;
 namespace {
 
 struct TestShortcutInfo {
+  std::string guid;
   std::string url;
   std::string title;  // The text that orginally was searched for.
   std::string contents;
@@ -40,62 +42,79 @@ struct TestShortcutInfo {
   int typed_count;
   int days_from_now;
 } shortcut_test_db[] = {
-  { "http://www.google.com/", "goog",
+  { "BD85DBA2-8C29-49F9-84AE-48E1E90880E0",
+    "http://www.google.com/", "goog",
     "Google", "0,1,4,0", "Google", "0,3,4,1", 100, 1 },
-  { "http://slashdot.org/", "slash",
+  { "BD85DBA2-8C29-49F9-84AE-48E1E90880E1",
+    "http://slashdot.org/", "slash",
     "slashdot.org", "0,3,5,1",
     "Slashdot - News for nerds, stuff that matters", "0,2,5,0", 100, 0},
-  { "http://slashdot.org/", "news",
+  { "BD85DBA2-8C29-49F9-84AE-48E1E90880E2",
+    "http://slashdot.org/", "news",
     "slashdot.org", "0,1",
     "Slashdot - News for nerds, stuff that matters", "0,0,11,2,15,0", 5, 0},
-  { "http://sports.yahoo.com/", "news",
+  { "BD85DBA2-8C29-49F9-84AE-48E1E90880E3",
+    "http://sports.yahoo.com/", "news",
     "sports.yahoo.com", "0,1",
     "Yahoo! Sports - Sports News, Scores, Rumors, Fantasy Games, and more",
     "0,0,23,2,27,0", 5, 2},
-  { "http://www.cnn.com/index.html", "news weather",
+  { "BD85DBA2-8C29-49F9-84AE-48E1E90880E4",
+    "http://www.cnn.com/index.html", "news weather",
     "www.cnn.com/index.html", "0,1",
     "CNN.com - Breaking News, U.S., World, Weather, Entertainment & Video",
     "0,0,19,2,23,0,38,2,45,0", 10, 1},
-  { "http://sports.yahoo.com/", "nhl scores",
+  { "BD85DBA2-8C29-49F9-84AE-48E1E90880E5",
+    "http://sports.yahoo.com/", "nhl scores",
     "sports.yahoo.com", "0,1",
     "Yahoo! Sports - Sports News, Scores, Rumors, Fantasy Games, and more",
     "0,0,29,2,35,0", 10, 1},
-  { "http://www.nhl.com/scores/index.html", "nhl scores",
+  { "BD85DBA2-8C29-49F9-84AE-48E1E90880E6",
+    "http://www.nhl.com/scores/index.html", "nhl scores",
     "www.nhl.com/scores/index.html", "0,1,4,3,7,1",
     "January 13, 2010 - NHL.com - Scores", "0,0,19,2,22,0,29,2,35,0", 1, 5},
-  { "http://www.testsite.com/a.html", "just",
+  { "BD85DBA2-8C29-49F9-84AE-48E1E90880E7",
+    "http://www.testsite.com/a.html", "just",
     "www.testsite.com/a.html", "0,1",
     "Test - site - just a test", "0,0,14,2,18,0", 1, 5},
-  { "http://www.testsite.com/b.html", "just",
+  { "BD85DBA2-8C29-49F9-84AE-48E1E90880E8",
+    "http://www.testsite.com/b.html", "just",
     "www.testsite.com/b.html", "0,1",
     "Test - site - just a test", "0,0,14,2,18,0", 2, 5},
-  { "http://www.testsite.com/c.html", "just",
+  { "BD85DBA2-8C29-49F9-84AE-48E1E90880E9",
+    "http://www.testsite.com/c.html", "just",
     "www.testsite.com/c.html", "0,1",
     "Test - site - just a test", "0,0,14,2,18,0", 1, 8},
-  { "http://www.testsite.com/d.html", "just a",
+  { "BD85DBA2-8C29-49F9-84AE-48E1E90880EA",
+    "http://www.testsite.com/d.html", "just a",
     "www.testsite.com/d.html", "0,1",
     "Test - site - just a test", "0,0,14,2,18,0", 1, 12},
-  { "http://www.testsite.com/e.html", "just a t",
+  { "BD85DBA2-8C29-49F9-84AE-48E1E90880EB",
+    "http://www.testsite.com/e.html", "just a t",
     "www.testsite.com/e.html", "0,1",
     "Test - site - just a test", "0,0,14,2,18,0", 1, 12},
-  { "http://www.testsite.com/f.html", "just a te",
+  { "BD85DBA2-8C29-49F9-84AE-48E1E90880EC",
+    "http://www.testsite.com/f.html", "just a te",
     "www.testsite.com/f.html", "0,1",
     "Test - site - just a test", "0,0,14,2,18,0", 1, 12},
-  { "http://www.daysagotest.com/a.html", "ago",
+  { "BD85DBA2-8C29-49F9-84AE-48E1E90880ED",
+    "http://www.daysagotest.com/a.html", "ago",
     "www.daysagotest.com/a.html", "0,1,8,3,11,1",
     "Test - site", "0,0", 1, 1},
-  { "http://www.daysagotest.com/b.html", "ago",
+  { "BD85DBA2-8C29-49F9-84AE-48E1E90880EE",
+    "http://www.daysagotest.com/b.html", "ago",
     "www.daysagotest.com/b.html", "0,1,8,3,11,1",
     "Test - site", "0,0", 1, 2},
-  { "http://www.daysagotest.com/c.html", "ago",
+  { "BD85DBA2-8C29-49F9-84AE-48E1E90880EF",
+    "http://www.daysagotest.com/c.html", "ago",
     "www.daysagotest.com/c.html", "0,1,8,3,11,1",
     "Test - site", "0,0", 1, 3},
-  { "http://www.daysagotest.com/d.html", "ago",
+  { "BD85DBA2-8C29-49F9-84AE-48E1E90880F0",
+    "http://www.daysagotest.com/d.html", "ago",
     "www.daysagotest.com/d.html", "0,1,8,3,11,1",
     "Test - site", "0,0", 1, 4},
 };
 
-}  // end namespace
+}  // namespace
 
 class ShortcutsProviderTest : public testing::Test,
                               public ACProviderListener {
@@ -139,6 +158,7 @@ class ShortcutsProviderTest : public testing::Test,
 
   ACMatches ac_matches_;  // The resulting matches after running RunTest.
 
+  scoped_refptr<history::ShortcutsBackend> mock_backend_;
   scoped_refptr<ShortcutsProvider> provider_;
 };
 
@@ -154,6 +174,9 @@ void ShortcutsProviderTest::SetUp() {
   profile_.reset(new TestingProfile());
   profile_->CreateHistoryService(true, false);
   provider_ = new ShortcutsProvider(this, profile_.get());
+  mock_backend_ = new history::ShortcutsBackend(FilePath(), profile_.get());
+  mock_backend_->Init();
+  provider_->set_shortcuts_backend(mock_backend_.get());
   FillData();
 }
 
@@ -163,7 +186,7 @@ void ShortcutsProviderTest::TearDown() {
 
 void ShortcutsProviderTest::FillData() {
   DCHECK(provider_.get());
-  provider_->shortcuts_map_.clear();
+  mock_backend_->DeleteAllShortcuts();
   for (size_t i = 0; i < arraysize(shortcut_test_db); ++i) {
     const TestShortcutInfo& cur = shortcut_test_db[i];
     const GURL current_url(cur.url);
@@ -177,8 +200,8 @@ void ShortcutsProviderTest::FillData() {
         shortcuts_provider::SpansFromString(
             ASCIIToUTF16(cur.description_class)));
     shortcut.last_access_time = visit_time;
-    provider_->shortcuts_map_.insert(std::make_pair(ASCIIToUTF16(cur.title),
-                                                    shortcut));
+    shortcut.id = cur.guid;
+    mock_backend_->AddShortcut(shortcut);
   }
 }
 
@@ -536,18 +559,22 @@ TEST_F(ShortcutsProviderTest, CalculateScore) {
 
 TEST_F(ShortcutsProviderTest, DeleteMatch) {
   TestShortcutInfo shortcuts_to_test_delete[3] = {
-    { "http://www.deletetest.com/1.html", "delete",
+    { "BD85DBA2-8C29-49F9-84AE-48E1E90880F1",
+      "http://www.deletetest.com/1.html", "delete",
       "http://www.deletetest.com/1.html", "0,2",
       "Erase this shortcut!", "0,0", 1, 1},
-    { "http://www.deletetest.com/1.html", "erase",
+    { "BD85DBA2-8C29-49F9-84AE-48E1E90880F2",
+      "http://www.deletetest.com/1.html", "erase",
       "http://www.deletetest.com/1.html", "0,2",
       "Erase this shortcut!", "0,0", 1, 1},
-    { "http://www.deletetest.com/2.html", "delete",
+    { "BD85DBA2-8C29-49F9-84AE-48E1E90880F3",
+      "http://www.deletetest.com/2.html", "delete",
       "http://www.deletetest.com/2.html", "0,2",
       "Erase this shortcut!", "0,0", 1, 1},
   };
 
-  size_t original_shortcuts_count = provider_->shortcuts_map_.size();
+  size_t original_shortcuts_count =
+      provider_->shortcuts_backend_->shortcuts_map().size();
 
   for (size_t i = 0; i < arraysize(shortcuts_to_test_delete); ++i) {
     const TestShortcutInfo& cur = shortcuts_to_test_delete[i];
@@ -562,15 +589,18 @@ TEST_F(ShortcutsProviderTest, DeleteMatch) {
         shortcuts_provider::SpansFromString(
             ASCIIToUTF16(cur.description_class)));
     shortcut.last_access_time = visit_time;
-    provider_->shortcuts_map_.insert(std::make_pair(ASCIIToUTF16(cur.title),
-                                                    shortcut));
+    shortcut.id = cur.guid;
+    mock_backend_->AddShortcut(shortcut);
   }
 
-  EXPECT_EQ(original_shortcuts_count + 3, provider_->shortcuts_map_.size());
-  EXPECT_FALSE(provider_->shortcuts_map_.end() ==
-               provider_->shortcuts_map_.find(ASCIIToUTF16("delete")));
-  EXPECT_FALSE(provider_->shortcuts_map_.end() ==
-               provider_->shortcuts_map_.find(ASCIIToUTF16("erase")));
+  EXPECT_EQ(original_shortcuts_count + 3,
+            provider_->shortcuts_backend_->shortcuts_map().size());
+  EXPECT_FALSE(provider_->shortcuts_backend_->shortcuts_map().end() ==
+               provider_->shortcuts_backend_->shortcuts_map().find(
+                   ASCIIToUTF16("delete")));
+  EXPECT_FALSE(provider_->shortcuts_backend_->shortcuts_map().end() ==
+               provider_->shortcuts_backend_->shortcuts_map().find(
+                   ASCIIToUTF16("erase")));
 
   AutocompleteMatch match(provider_, 1200, true,
                           AutocompleteMatch::HISTORY_TITLE);
@@ -583,18 +613,23 @@ TEST_F(ShortcutsProviderTest, DeleteMatch) {
 
   // |shortcuts_to_test_delete[0]| and |shortcuts_to_test_delete[1]| should be
   // deleted, but not |shortcuts_to_test_delete[2]| as it has different url.
-  EXPECT_EQ(original_shortcuts_count + 1, provider_->shortcuts_map_.size());
-  EXPECT_FALSE(provider_->shortcuts_map_.end() ==
-               provider_->shortcuts_map_.find(ASCIIToUTF16("delete")));
-  EXPECT_TRUE(provider_->shortcuts_map_.end() ==
-              provider_->shortcuts_map_.find(ASCIIToUTF16("erase")));
+  EXPECT_EQ(original_shortcuts_count + 1,
+            provider_->shortcuts_backend_->shortcuts_map().size());
+  EXPECT_FALSE(provider_->shortcuts_backend_->shortcuts_map().end() ==
+               provider_->shortcuts_backend_->shortcuts_map().find(
+                   ASCIIToUTF16("delete")));
+  EXPECT_TRUE(provider_->shortcuts_backend_->shortcuts_map().end() ==
+              provider_->shortcuts_backend_->shortcuts_map().find(
+                  ASCIIToUTF16("erase")));
 
   match.destination_url = GURL(shortcuts_to_test_delete[2].url);
   match.contents = ASCIIToUTF16(shortcuts_to_test_delete[2].contents);
   match.description = ASCIIToUTF16(shortcuts_to_test_delete[2].description);
 
   provider_->DeleteMatch(match);
-  EXPECT_EQ(original_shortcuts_count, provider_->shortcuts_map_.size());
-  EXPECT_TRUE(provider_->shortcuts_map_.end() ==
-              provider_->shortcuts_map_.find(ASCIIToUTF16("delete")));
+  EXPECT_EQ(original_shortcuts_count,
+            provider_->shortcuts_backend_->shortcuts_map().size());
+  EXPECT_TRUE(provider_->shortcuts_backend_->shortcuts_map().end() ==
+              provider_->shortcuts_backend_->shortcuts_map().find(
+                  ASCIIToUTF16("delete")));
 }
diff --git a/chrome/browser/history/shortcuts_backend.cc b/chrome/browser/history/shortcuts_backend.cc
index 9c8d2ca..6505027 100644
--- a/chrome/browser/history/shortcuts_backend.cc
+++ b/chrome/browser/history/shortcuts_backend.cc
@@ -28,8 +28,8 @@ namespace history {
 ShortcutsBackend::ShortcutsBackend(const FilePath& db_folder_path,
                                    Profile *profile)
     : current_state_(NOT_INITIALIZED),
-      observer_list_(new ObserverListThreadSafe<ShortcutsBackendObserver>()),
-      db_(db_folder_path) {
+      db_(new ShortcutsDatabase(db_folder_path)),
+      no_db_access_(db_folder_path.empty()) {
   // |profile| can be NULL in tests.
   if (profile) {
     notification_registrar_.Add(this, chrome::NOTIFICATION_OMNIBOX_OPENED_URL,
@@ -42,146 +42,151 @@ ShortcutsBackend::ShortcutsBackend(const FilePath& db_folder_path,
 ShortcutsBackend::~ShortcutsBackend() {}
 
 bool ShortcutsBackend::Init() {
-  if (base::subtle::NoBarrier_CompareAndSwap(&current_state_,
-                                             NOT_INITIALIZED,
-                                             INITIALIZING) == NOT_INITIALIZED) {
-    return BrowserThread::PostTask(BrowserThread::DB, FROM_HERE,
-        NewRunnableMethod(this, &ShortcutsBackend::InitInternal));
+  if (current_state_ == NOT_INITIALIZED) {
+    current_state_ = INITIALIZING;
+    if (no_db_access_) {
+      current_state_ = INITIALIZED;
+      return true;
+    } else {
+      return BrowserThread::PostTask(BrowserThread::DB, FROM_HERE,
+          NewRunnableMethod(this, &ShortcutsBackend::InitInternal));
+    }
   } else {
     return false;
   }
 }
 
-bool ShortcutsBackend::AddShortcut(shortcuts_provider::Shortcut shortcut) {
-  // It is safe to add a shortcut while the backend is being initialized since
-  // the addition will occur on the same thread as the initialization.
-  DCHECK(current_state_ != NOT_INITIALIZED);
+bool ShortcutsBackend::AddShortcut(
+    const shortcuts_provider::Shortcut& shortcut) {
+  if (!initialized())
+    return false;
+  DCHECK(guid_map_.find(shortcut.id) == guid_map_.end());
+  guid_map_[shortcut.id] = shortcuts_map_.insert(
+      std::make_pair(base::i18n::ToLower(shortcut.text), shortcut));
+  FOR_EACH_OBSERVER(ShortcutsBackendObserver, observer_list_,
+                    OnShortcutsChanged());
+  if (no_db_access_)
+    return true;
   return BrowserThread::PostTask(BrowserThread::DB, FROM_HERE,
-      NewRunnableMethod(this, &ShortcutsBackend::AddOrUpdateShortcutInternal,
-                        shortcut, true));
+      NewRunnableMethod(db_.get(), &ShortcutsDatabase::AddShortcut, shortcut));
 }
 
-bool ShortcutsBackend::UpdateShortcut(shortcuts_provider::Shortcut shortcut) {
-  DCHECK(initialized());
+bool ShortcutsBackend::UpdateShortcut(
+    const shortcuts_provider::Shortcut& shortcut) {
+  if (!initialized())
+    return false;
+  shortcuts_provider::GuidToShortcutsIteratorMap::iterator it =
+      guid_map_.find(shortcut.id);
+  if (it != guid_map_.end())
+    shortcuts_map_.erase(it->second);
+  guid_map_[shortcut.id] = shortcuts_map_.insert(
+      std::make_pair(base::i18n::ToLower(shortcut.text), shortcut));
+  FOR_EACH_OBSERVER(ShortcutsBackendObserver, observer_list_,
+                    OnShortcutsChanged());
+  if (no_db_access_)
+    return true;
   return BrowserThread::PostTask(BrowserThread::DB, FROM_HERE,
-      NewRunnableMethod(this, &ShortcutsBackend::AddOrUpdateShortcutInternal,
-                        shortcut, false));
+      NewRunnableMethod(db_.get(), &ShortcutsDatabase::UpdateShortcut,
+                        shortcut));
 }
 
 bool ShortcutsBackend::DeleteShortcutsWithIds(
     const std::vector<std::string>& shortcut_ids) {
-  DCHECK(initialized());
+  if (!initialized())
+    return false;
+  for (size_t i = 0; i < shortcut_ids.size(); ++i) {
+    shortcuts_provider::GuidToShortcutsIteratorMap::iterator it =
+        guid_map_.find(shortcut_ids[i]);
+    if (it != guid_map_.end()) {
+      shortcuts_map_.erase(it->second);
+      guid_map_.erase(it);
+    }
+  }
+  FOR_EACH_OBSERVER(ShortcutsBackendObserver, observer_list_,
+                    OnShortcutsChanged());
+  if (no_db_access_)
+    return true;
   return BrowserThread::PostTask(BrowserThread::DB, FROM_HERE,
-      NewRunnableMethod(this, &ShortcutsBackend::DeleteShortcutsWithIdsInternal,
+      NewRunnableMethod(db_.get(), &ShortcutsDatabase::DeleteShortcutsWithIds,
                         shortcut_ids));
 }
 
 bool ShortcutsBackend::DeleteShortcutsWithUrl(const GURL& shortcut_url) {
-  DCHECK(initialized());
+  if (!initialized())
+    return false;
+  std::vector<std::string> shortcut_ids;
+  for (shortcuts_provider::GuidToShortcutsIteratorMap::iterator
+           it = guid_map_.begin();
+       it != guid_map_.end();) {
+    if (it->second->second.url == shortcut_url) {
+      shortcut_ids.push_back(it->first);
+      shortcuts_map_.erase(it->second);
+      guid_map_.erase(it++);
+    } else {
+      ++it;
+    }
+  }
+  FOR_EACH_OBSERVER(ShortcutsBackendObserver, observer_list_,
+                    OnShortcutsChanged());
+  if (no_db_access_)
+    return true;
   return BrowserThread::PostTask(BrowserThread::DB, FROM_HERE,
-      NewRunnableMethod(this, &ShortcutsBackend::DeleteShortcutsWithUrlInternal,
+      NewRunnableMethod(db_.get(), &ShortcutsDatabase::DeleteShortcutsWithUrl,
                         shortcut_url.spec()));
 }
 
-bool ShortcutsBackend::GetShortcuts(
-    shortcuts_provider::ShortcutMap* shortcuts) {
-  DCHECK(initialized());
-  DCHECK(shortcuts);
-
+bool ShortcutsBackend::DeleteAllShortcuts() {
   if (!initialized())
     return false;
-  shortcuts->clear();
-  base::AutoLock lock(data_access_lock_);
-  shortcuts->insert(shortcuts_map_.begin(), shortcuts_map_.end());
-  return true;
+  shortcuts_map_.clear();
+  guid_map_.clear();
+  FOR_EACH_OBSERVER(ShortcutsBackendObserver, observer_list_,
+                    OnShortcutsChanged());
+  if (no_db_access_)
+    return true;
+  return BrowserThread::PostTask(BrowserThread::DB, FROM_HERE,
+      NewRunnableMethod(db_.get(), &ShortcutsDatabase::DeleteAllShortcuts));
 }
 
 void ShortcutsBackend::InitInternal() {
-  db_.Init();
+  DCHECK(current_state_ == INITIALIZING);
+  db_->Init();
   shortcuts_provider::GuidToShortcutMap shortcuts;
-  db_.LoadShortcuts(&shortcuts);
+  db_->LoadShortcuts(&shortcuts);
+  temp_shortcuts_map_.reset(new shortcuts_provider::ShortcutMap);
+  temp_guid_map_.reset(new shortcuts_provider::GuidToShortcutsIteratorMap);
   for (shortcuts_provider::GuidToShortcutMap::iterator it = shortcuts.begin();
        it != shortcuts.end(); ++it) {
-    guid_map_[it->first] = shortcuts_map_.insert(
+    (*temp_guid_map_)[it->first] = temp_shortcuts_map_->insert(
         std::make_pair(base::i18n::ToLower(it->second.text), it->second));
   }
-  base::subtle::NoBarrier_CompareAndSwap(&current_state_, INITIALIZING,
-                                         INITIALIZED);
-  observer_list_->Notify(&ShortcutsBackendObserver::OnShortcutsLoaded);
-}
-
-void ShortcutsBackend::AddOrUpdateShortcutInternal(
-    shortcuts_provider::Shortcut shortcut, bool add) {
-  {
-    // Update local copy.
-    base::AutoLock lock(data_access_lock_);
-    shortcuts_provider::GuidToShortcutsIteratorMap::iterator it =
-        guid_map_.find(shortcut.id);
-    if (it != guid_map_.end())
-      shortcuts_map_.erase(it->second);
-    guid_map_[shortcut.id] = shortcuts_map_.insert(
-        std::make_pair(base::i18n::ToLower(shortcut.text), shortcut));
-  }
-  if (add)
-    db_.AddShortcut(shortcut);
-  else
-    db_.UpdateShortcut(shortcut);
-  observer_list_->Notify(&ShortcutsBackendObserver::OnShortcutAddedOrUpdated,
-                         shortcut);
-}
-
-void ShortcutsBackend::DeleteShortcutsWithIdsInternal(
-    std::vector<std::string> shortcut_ids) {
-  {
-    // Update local copy.
-    base::AutoLock lock(data_access_lock_);
-    for (size_t i = 0; i < shortcut_ids.size(); ++i) {
-      shortcuts_provider::GuidToShortcutsIteratorMap::iterator it =
-          guid_map_.find(shortcut_ids[i]);
-      if (it != guid_map_.end()) {
-        shortcuts_map_.erase(it->second);
-        guid_map_.erase(it);
-      }
-    }
-  }
-  db_.DeleteShortcutsWithIds(shortcut_ids);
-  observer_list_->Notify(&ShortcutsBackendObserver::OnShortcutsRemoved,
-                         shortcut_ids);
+  BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
+      NewRunnableMethod(this, &ShortcutsBackend::InitCompleted));
 }
 
-void ShortcutsBackend::DeleteShortcutsWithUrlInternal(
-    std::string shortcut_url) {
-  std::vector<std::string> shortcut_ids;
-  {
-    // Update local copy.
-    base::AutoLock lock(data_access_lock_);
-    for (shortcuts_provider::GuidToShortcutsIteratorMap::iterator
-             it = guid_map_.begin();
-         it != guid_map_.end();) {
-      if (it->second->second.url.spec() == shortcut_url) {
-        shortcut_ids.push_back(it->first);
-        shortcuts_map_.erase(it->second);
-        guid_map_.erase(it++);
-      } else {
-        ++it;
-      }
-    }
-  }
-  db_.DeleteShortcutsWithUrl(shortcut_url);
-  observer_list_->Notify(&ShortcutsBackendObserver::OnShortcutsRemoved,
-                         shortcut_ids);
+void ShortcutsBackend::InitCompleted() {
+  temp_guid_map_->swap(guid_map_);
+  temp_shortcuts_map_->swap(shortcuts_map_);
+  temp_shortcuts_map_.reset(NULL);
+  temp_guid_map_.reset(NULL);
+  current_state_ = INITIALIZED;
+  FOR_EACH_OBSERVER(ShortcutsBackendObserver, observer_list_,
+                    OnShortcutsLoaded());
 }
 
 // NotificationObserver:
 void ShortcutsBackend::Observe(int type,
                                const NotificationSource& source,
                                const NotificationDetails& details) {
+  if (current_state_ != INITIALIZED)
+    return;
   if (type == chrome::NOTIFICATION_HISTORY_URLS_DELETED) {
+    if (Details<const history::URLsDeletedDetails>(details)->all_history)
+      DeleteAllShortcuts();
     const std::set<GURL>& urls =
         Details<const history::URLsDeletedDetails>(details)->urls;
     std::vector<std::string> shortcut_ids;
 
-    base::AutoLock lock(data_access_lock_);
     for (shortcuts_provider::GuidToShortcutsIteratorMap::iterator
              it = guid_map_.begin();
          it != guid_map_.end(); ++it) {
@@ -200,7 +205,6 @@ void ShortcutsBackend::Observe(int type,
   int number_of_hits = 1;
   std::string id;
   const AutocompleteMatch& match(log->result.match_at(log->selected_index));
-  base::AutoLock lock(data_access_lock_);
   for (shortcuts_provider::ShortcutMap::iterator it =
            shortcuts_map_.lower_bound(text_lowercase);
        it != shortcuts_map_.end() &&
@@ -208,8 +212,6 @@ void ShortcutsBackend::Observe(int type,
     if (match.destination_url == it->second.url) {
       number_of_hits = it->second.number_of_hits + 1;
       id = it->second.id;
-      // guid_map_ will be updated further down on re-insertion.
-      shortcuts_map_.erase(it);
       break;
     }
   }
@@ -222,9 +224,6 @@ void ShortcutsBackend::Observe(int type,
   else
     shortcut.id = id;
 
-  guid_map_[shortcut.id] = shortcuts_map_.insert(
-      std::make_pair(text_lowercase, shortcut));
-
   if (number_of_hits == 1)
     AddShortcut(shortcut);
   else
diff --git a/chrome/browser/history/shortcuts_backend.h b/chrome/browser/history/shortcuts_backend.h
index abaccd3..67bf64e 100644
--- a/chrome/browser/history/shortcuts_backend.h
+++ b/chrome/browser/history/shortcuts_backend.h
@@ -10,12 +10,11 @@
 #include <string>
 #include <vector>
 
-#include "base/atomicops.h"
 #include "base/file_path.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
-#include "base/observer_list_threadsafe.h"
+#include "base/observer_list.h"
 #include "base/string16.h"
 #include "base/synchronization/lock.h"
 #include "chrome/browser/autocomplete/shortcuts_provider_shortcut.h"
@@ -34,7 +33,8 @@ class ShortcutsBackend : public base::RefCountedThreadSafe<ShortcutsBackend>,
                          public NotificationObserver {
  public:
   // |profile| is necessary for profile notifications only and can be NULL in
-  // unit-tests.
+  // unit-tests. |db_folder_path| could be an empty path only in unit-tests as
+  // well. It means there is no database created, all things are done in memory.
   ShortcutsBackend(const FilePath& db_folder_path, Profile* profile);
   virtual ~ShortcutsBackend();
 
@@ -44,13 +44,8 @@ class ShortcutsBackend : public base::RefCountedThreadSafe<ShortcutsBackend>,
    public:
     // Called after the database is loaded and Init() completed.
     virtual void OnShortcutsLoaded() = 0;
-    // This callback is called when addition or change was processed by the
-    // database.
-    virtual void OnShortcutAddedOrUpdated(
-        const shortcuts_provider::Shortcut& shortcut) = 0;
-    // Called when shortcuts are removed from the database.
-    virtual void OnShortcutsRemoved(
-        const std::vector<std::string>& shortcut_ids) = 0;
+    // Called when shortcuts changed (added/updated/removed) in the database.
+    virtual void OnShortcutsChanged() {}
    protected:
     virtual ~ShortcutsBackendObserver() {}
   };
@@ -61,11 +56,13 @@ class ShortcutsBackend : public base::RefCountedThreadSafe<ShortcutsBackend>,
 
   bool initialized() const { return current_state_ == INITIALIZED; }
 
+  // All of the public functions *must* be called on UI thread only!
+
   // Adds the Shortcut to the database.
-  bool AddShortcut(shortcuts_provider::Shortcut shortcut);
+  bool AddShortcut(const shortcuts_provider::Shortcut& shortcut);
 
   // Updates timing and selection count for the Shortcut.
-  bool UpdateShortcut(shortcuts_provider::Shortcut shortcut);
+  bool UpdateShortcut(const shortcuts_provider::Shortcut& shortcut);
 
   // Deletes the Shortcuts with the id.
   bool DeleteShortcutsWithIds(const std::vector<std::string>& shortcut_ids);
@@ -73,35 +70,32 @@ class ShortcutsBackend : public base::RefCountedThreadSafe<ShortcutsBackend>,
   // Deletes the Shortcuts with the url.
   bool DeleteShortcutsWithUrl(const GURL& shortcut_url);
 
-  // Replaces the contents of |shortcuts| with the backend's from the database.
-  bool GetShortcuts(shortcuts_provider::ShortcutMap* shortcuts);
+  // Deletes all of the shortcuts.
+  bool DeleteAllShortcuts();
+
+  const shortcuts_provider::ShortcutMap& shortcuts_map() const {
+    return shortcuts_map_;
+  }
+
+  const shortcuts_provider::GuidToShortcutsIteratorMap& guid_map() const {
+    return guid_map_;
+  }
 
   void AddObserver(ShortcutsBackendObserver* obs) {
-    observer_list_->AddObserver(obs);
+    observer_list_.AddObserver(obs);
   }
 
   void RemoveObserver(ShortcutsBackendObserver* obs) {
-    observer_list_->RemoveObserver(obs);
+    observer_list_.RemoveObserver(obs);
   }
 
  private:
   // Internal initialization of the back-end. Posted by Init() to the DB thread.
-  // On completion notifies all back-end observers asyncronously on their own
-  // thread.
+  // On completion posts InitCompleted() back to UI thread.
   void InitInternal();
-  // Internal addition or update of a shortcut. Posted by AddShortcut() or
-  // UpdateShortcut() to the DB thread. On completion notifies all back-end
-  // observers asyncronously on their own thread.
-  void AddOrUpdateShortcutInternal(shortcuts_provider::Shortcut shortcut,
-                                   bool add);
-  // Internal deletion of shortcuts. Posted by DeleteShortcutsWithIds() to the
-  // DB thread. On completion notifies all back-end observers asyncronously on
-  // their own thread.
-  void DeleteShortcutsWithIdsInternal(std::vector<std::string> shortcut_ids);
-  // Internal deletion of shortcut with the url. Posted by
-  // DeleteShortcutsWithUrl() to the DB thread. On completion notifies all
-  // back-end observers asyncronously on their own thread.
-  void DeleteShortcutsWithUrlInternal(std::string shortcut_url);
+
+  // Finishes initialization on UI thread, notifies all observers.
+  void InitCompleted();
 
   // NotificationObserver:
   virtual void Observe(int type,
@@ -114,20 +108,25 @@ class ShortcutsBackend : public base::RefCountedThreadSafe<ShortcutsBackend>,
     INITIALIZED,  // Initialization completed, all accessors can be safely
                   // called.
   };
-  // |current_state_| has values of CurrentState enum.
-  volatile base::subtle::Atomic32 current_state_;
-  scoped_refptr<ObserverListThreadSafe<ShortcutsBackendObserver> >
-      observer_list_;
-  ShortcutsDatabase db_;
+  CurrentState current_state_;
+  ObserverList<ShortcutsBackendObserver> observer_list_;
+  scoped_refptr<ShortcutsDatabase> db_;
+
+  // The |temp_shortcuts_map_| and |temp_guid_map_| used for temporary storage
+  // between InitInternal() and InitComplete() to avoid doing a potentially huge
+  // copy.
+  scoped_ptr<shortcuts_provider::ShortcutMap> temp_shortcuts_map_;
+  scoped_ptr<shortcuts_provider::GuidToShortcutsIteratorMap> temp_guid_map_;
 
   shortcuts_provider::ShortcutMap shortcuts_map_;
   // This is a helper map for quick access to a shortcut by guid.
   shortcuts_provider::GuidToShortcutsIteratorMap guid_map_;
 
-  base::Lock data_access_lock_;
-
   NotificationRegistrar notification_registrar_;
 
+  // For some unit-test only.
+  bool no_db_access_;
+
   DISALLOW_COPY_AND_ASSIGN(ShortcutsBackend);
 };
 
diff --git a/chrome/browser/history/shortcuts_backend_unittest.cc b/chrome/browser/history/shortcuts_backend_unittest.cc
index 0bad07c..cc38425 100644
--- a/chrome/browser/history/shortcuts_backend_unittest.cc
+++ b/chrome/browser/history/shortcuts_backend_unittest.cc
@@ -36,9 +36,7 @@ class ShortcutsBackendTest : public testing::Test,
   void TearDown();
 
   virtual void OnShortcutsLoaded() OVERRIDE;
-  virtual void OnShortcutAddedOrUpdated(const Shortcut& shortcut) OVERRIDE;
-  virtual void OnShortcutsRemoved(
-      const std::vector<std::string>& shortcut_ids) OVERRIDE;
+  virtual void OnShortcutsChanged() OVERRIDE;
 
   void InitBackend();
 
@@ -49,8 +47,6 @@ class ShortcutsBackendTest : public testing::Test,
   BrowserThread db_thread_;
 
   bool load_notified_;
-  Shortcut notified_shortcut_;
-  std::vector<std::string> notified_shortcut_ids_;
 };
 
 void ShortcutsBackendTest::SetUp() {
@@ -70,15 +66,7 @@ void ShortcutsBackendTest::OnShortcutsLoaded() {
   MessageLoop::current()->Quit();
 }
 
-void ShortcutsBackendTest::OnShortcutAddedOrUpdated(const Shortcut& shortcut) {
-  notified_shortcut_ = shortcut;
-  MessageLoop::current()->Quit();
-}
-
-void ShortcutsBackendTest::OnShortcutsRemoved(
-    const std::vector<std::string>& shortcut_ids) {
-  notified_shortcut_ids_ = shortcut_ids;
-  MessageLoop::current()->Quit();
+void ShortcutsBackendTest::OnShortcutsChanged() {
 }
 
 void ShortcutsBackendTest::InitBackend() {
@@ -90,7 +78,6 @@ void ShortcutsBackendTest::InitBackend() {
   EXPECT_TRUE(backend_->initialized());
 }
 
-
 TEST_F(ShortcutsBackendTest, AddAndUpdateShortcut) {
   InitBackend();
   Shortcut shortcut("BD85DBA2-8C29-49F9-84AE-48E1E90880DF",
@@ -100,14 +87,15 @@ TEST_F(ShortcutsBackendTest, AddAndUpdateShortcut) {
                     base::Time::Now().ToInternalValue(),
                     100);
   EXPECT_TRUE(backend_->AddShortcut(shortcut));
-  MessageLoop::current()->Run();
-  EXPECT_EQ(shortcut.id, notified_shortcut_.id);
-  EXPECT_EQ(shortcut.contents, notified_shortcut_.contents);
+
+  const ShortcutMap& shortcuts = backend_->shortcuts_map();
+  ASSERT_TRUE(shortcuts.end() != shortcuts.find(shortcut.text));
+  EXPECT_EQ(shortcut.id, shortcuts.find(shortcut.text)->second.id);
+  EXPECT_EQ(shortcut.contents, shortcuts.find(shortcut.text)->second.contents);
   shortcut.contents = ASCIIToUTF16("Google Web Search");
   EXPECT_TRUE(backend_->UpdateShortcut(shortcut));
-  MessageLoop::current()->Run();
-  EXPECT_EQ(shortcut.id, notified_shortcut_.id);
-  EXPECT_EQ(shortcut.contents, notified_shortcut_.contents);
+  EXPECT_EQ(shortcut.id, shortcuts.find(shortcut.text)->second.id);
+  EXPECT_EQ(shortcut.contents, shortcuts.find(shortcut.text)->second.contents);
 }
 
 TEST_F(ShortcutsBackendTest, DeleteShortcuts) {
@@ -120,7 +108,6 @@ TEST_F(ShortcutsBackendTest, DeleteShortcuts) {
                      base::Time::Now().ToInternalValue(),
                      100);
   EXPECT_TRUE(backend_->AddShortcut(shortcut1));
-  MessageLoop::current()->Run();
 
   Shortcut shortcut2("BD85DBA2-8C29-49F9-84AE-48E1E90880E0",
                      ASCIIToUTF16("gle"), ASCIIToUTF16("http://www.google.com"),
@@ -129,7 +116,6 @@ TEST_F(ShortcutsBackendTest, DeleteShortcuts) {
                      base::Time::Now().ToInternalValue(),
                      100);
   EXPECT_TRUE(backend_->AddShortcut(shortcut2));
-  MessageLoop::current()->Run();
 
   Shortcut shortcut3("BD85DBA2-8C29-49F9-84AE-48E1E90880E1",
                      ASCIIToUTF16("sp"), ASCIIToUTF16("http://www.sport.com"),
@@ -138,7 +124,6 @@ TEST_F(ShortcutsBackendTest, DeleteShortcuts) {
                      base::Time::Now().ToInternalValue(),
                      10);
   EXPECT_TRUE(backend_->AddShortcut(shortcut3));
-  MessageLoop::current()->Run();
 
   Shortcut shortcut4("BD85DBA2-8C29-49F9-84AE-48E1E90880E2",
                      ASCIIToUTF16("mov"), ASCIIToUTF16("http://www.film.com"),
@@ -147,11 +132,8 @@ TEST_F(ShortcutsBackendTest, DeleteShortcuts) {
                      base::Time::Now().ToInternalValue(),
                      10);
   EXPECT_TRUE(backend_->AddShortcut(shortcut4));
-  MessageLoop::current()->Run();
-
-  ShortcutMap shortcuts;
 
-  EXPECT_TRUE(backend_->GetShortcuts(&shortcuts));
+  const ShortcutMap& shortcuts = backend_->shortcuts_map();
 
   ASSERT_EQ(4U, shortcuts.size());
   EXPECT_EQ(shortcut1.id, shortcuts.find(shortcut1.text)->second.id);
@@ -160,17 +142,12 @@ TEST_F(ShortcutsBackendTest, DeleteShortcuts) {
   EXPECT_EQ(shortcut4.id, shortcuts.find(shortcut4.text)->second.id);
 
   EXPECT_TRUE(backend_->DeleteShortcutsWithUrl(shortcut1.url));
-  MessageLoop::current()->Run();
-
-  ASSERT_EQ(2U, notified_shortcut_ids_.size());
-  EXPECT_TRUE(notified_shortcut_ids_[0] == shortcut1.id ||
-              notified_shortcut_ids_[1] == shortcut1.id);
-  EXPECT_TRUE(notified_shortcut_ids_[0] == shortcut2.id ||
-              notified_shortcut_ids_[1] == shortcut2.id);
-
-  EXPECT_TRUE(backend_->GetShortcuts(&shortcuts));
 
   ASSERT_EQ(2U, shortcuts.size());
+  EXPECT_TRUE(shortcuts.end() == shortcuts.find(shortcut1.text));
+  EXPECT_TRUE(shortcuts.end() == shortcuts.find(shortcut2.text));
+  ASSERT_TRUE(shortcuts.end() != shortcuts.find(shortcut3.text));
+  ASSERT_TRUE(shortcuts.end() != shortcuts.find(shortcut4.text));
   EXPECT_EQ(shortcut3.id, shortcuts.find(shortcut3.text)->second.id);
   EXPECT_EQ(shortcut4.id, shortcuts.find(shortcut4.text)->second.id);
 
@@ -179,13 +156,6 @@ TEST_F(ShortcutsBackendTest, DeleteShortcuts) {
   deleted_ids.push_back(shortcut4.id);
 
   EXPECT_TRUE(backend_->DeleteShortcutsWithIds(deleted_ids));
-  MessageLoop::current()->Run();
-
-  ASSERT_EQ(2U, notified_shortcut_ids_.size());
-  EXPECT_EQ(notified_shortcut_ids_[0], deleted_ids[0]);
-  EXPECT_EQ(notified_shortcut_ids_[1], deleted_ids[1]);
-
-  EXPECT_TRUE(backend_->GetShortcuts(&shortcuts));
 
   ASSERT_EQ(0U, shortcuts.size());
 }
diff --git a/chrome/browser/history/shortcuts_database.cc b/chrome/browser/history/shortcuts_database.cc
index f400e5c..45e11a9 100644
--- a/chrome/browser/history/shortcuts_database.cc
+++ b/chrome/browser/history/shortcuts_database.cc
@@ -21,7 +21,8 @@ using base::Time;
 
 namespace {
 
-const char *kShortcutsDBName = "omni_box_shortcuts";
+// Using define instead of const char, so I could use ## in the statements.
+#define kShortcutsDBName "omni_box_shortcuts"
 
 // The maximum length allowed for form data.
 const size_t kMaxDataLength = 2048;  // 2K is a hard limit on URLs URI.
@@ -103,32 +104,18 @@ bool ShortcutsDatabase::Init() {
   if (!db_.Open(database_path_))
     return false;
 
-  if (!db_.DoesTableExist(kShortcutsDBName)) {
-    if (!db_.Execute(base::StringPrintf(
-                     "CREATE TABLE %s ( "
-                     "id VARCHAR PRIMARY KEY, "
-                     "text VARCHAR, "
-                     "url VARCHAR, "
-                     "contents VARCHAR, "
-                     "contents_class VARCHAR, "
-                     "description VARCHAR, "
-                     "description_class VARCHAR, "
-                     "last_access_time INTEGER, "
-                     "number_of_hits INTEGER)", kShortcutsDBName).c_str())) {
-      NOTREACHED();
-      return false;
-    }
-  }
+  if (!EnsureTable())
+    return false;
   return true;
 }
 
 bool ShortcutsDatabase::AddShortcut(
-    const shortcuts_provider::Shortcut &shortcut) {
-  sql::Statement s(db_.GetUniqueStatement(base::StringPrintf(
-      "INSERT INTO %s"
+    const shortcuts_provider::Shortcut& shortcut) {
+  sql::Statement s(db_.GetCachedStatement(SQL_FROM_HERE,
+      "INSERT INTO " kShortcutsDBName
       " (id, text, url, contents, contents_class, description,"
       " description_class, last_access_time, number_of_hits) "
-      "VALUES (?,?,?,?,?,?,?,?,?)", kShortcutsDBName).c_str()));
+      "VALUES (?,?,?,?,?,?,?,?,?)"));
   if (!s) {
     NOTREACHED();
     return false;
@@ -143,13 +130,13 @@ bool ShortcutsDatabase::AddShortcut(
 }
 
 bool ShortcutsDatabase::UpdateShortcut(
-    const shortcuts_provider::Shortcut &shortcut) {
-  sql::Statement s(db_.GetUniqueStatement(base::StringPrintf(
-      "UPDATE %s "
+    const shortcuts_provider::Shortcut& shortcut) {
+  sql::Statement s(db_.GetCachedStatement(SQL_FROM_HERE,
+    "UPDATE " kShortcutsDBName " "
       "SET id=?, text=?, url=?, contents=?, contents_class=?,"
       "     description=?, description_class=?, last_access_time=?,"
       "     number_of_hits=? "
-      "WHERE id=?", kShortcutsDBName).c_str()));
+      "WHERE id=?"));
   if (!s) {
     NOTREACHED() << "Statement prepare failed";
     return false;
@@ -180,15 +167,29 @@ bool ShortcutsDatabase::DeleteShortcutsWithUrl(
   return DeleteShortcut("url", shortcut_url_spec, db_);
 }
 
+bool ShortcutsDatabase::DeleteAllShortcuts() {
+  sql::Statement s(db_.GetCachedStatement(SQL_FROM_HERE,
+      "DROP TABLE " kShortcutsDBName));
+  if (!s) {
+    NOTREACHED() << "Statement prepare failed";
+    return false;
+  }
+
+  if (!s.Run())
+    return false;
+  EnsureTable();
+  db_.Execute("VACUUM");
+  return true;
+}
 
 // Loads all of the shortcuts.
 bool ShortcutsDatabase::LoadShortcuts(
     std::map<std::string, shortcuts_provider::Shortcut>* shortcuts) {
   DCHECK(shortcuts);
-  sql::Statement s(db_.GetUniqueStatement(base::StringPrintf(
+  sql::Statement s(db_.GetCachedStatement(SQL_FROM_HERE,
       "SELECT id, text, url, contents, contents_class, "
       "description, description_class, last_access_time, number_of_hits "
-      "FROM %s", kShortcutsDBName).c_str()));
+      "FROM " kShortcutsDBName));
   if (!s) {
     NOTREACHED() << "Statement prepare failed";
     return false;
@@ -201,4 +202,24 @@ bool ShortcutsDatabase::LoadShortcuts(
   return true;
 }
 
+bool ShortcutsDatabase::EnsureTable() {
+  if (!db_.DoesTableExist(kShortcutsDBName)) {
+    if (!db_.Execute(base::StringPrintf(
+                     "CREATE TABLE %s ( "
+                     "id VARCHAR PRIMARY KEY, "
+                     "text VARCHAR, "
+                     "url VARCHAR, "
+                     "contents VARCHAR, "
+                     "contents_class VARCHAR, "
+                     "description VARCHAR, "
+                     "description_class VARCHAR, "
+                     "last_access_time INTEGER, "
+                     "number_of_hits INTEGER)", kShortcutsDBName).c_str())) {
+      NOTREACHED();
+      return false;
+    }
+  }
+  return true;
+}
+
 }  // namespace history
diff --git a/chrome/browser/history/shortcuts_database.h b/chrome/browser/history/shortcuts_database.h
index 3cbae58..4cd1fe5 100644
--- a/chrome/browser/history/shortcuts_database.h
+++ b/chrome/browser/history/shortcuts_database.h
@@ -12,6 +12,7 @@
 
 #include "base/file_path.h"
 #include "base/gtest_prod_util.h"
+#include "base/memory/ref_counted.h"
 #include "base/string16.h"
 #include "chrome/browser/autocomplete/shortcuts_provider_shortcut.h"
 #include "googleurl/src/gurl.h"
@@ -37,7 +38,7 @@ namespace history {
 //   last_access_time    Time the entry was accessed last, stored in seconds,
 //                       UTC.
 //   number_of_hits      Number of times that the entry has been selected.
-class ShortcutsDatabase {
+class ShortcutsDatabase : public base::RefCountedThreadSafe<ShortcutsDatabase> {
  public:
   explicit ShortcutsDatabase(const FilePath& folder_path);
   virtual ~ShortcutsDatabase();
@@ -45,10 +46,10 @@ class ShortcutsDatabase {
   bool Init();
 
   // Adds the ShortcutsProvider::Shortcut to the database.
-  bool AddShortcut(const shortcuts_provider::Shortcut &shortcut);
+  bool AddShortcut(const shortcuts_provider::Shortcut& shortcut);
 
   // Updates timing and selection count for the ShortcutsProvider::Shortcut.
-  bool UpdateShortcut(const shortcuts_provider::Shortcut &shortcut);
+  bool UpdateShortcut(const shortcuts_provider::Shortcut& shortcut);
 
   // Deletes the ShortcutsProvider::Shortcuts with the id.
   bool DeleteShortcutsWithIds(const std::vector<std::string>& shortcut_ids);
@@ -56,11 +57,17 @@ class ShortcutsDatabase {
   // Deletes the ShortcutsProvider::Shortcuts with the url.
   bool DeleteShortcutsWithUrl(const std::string& shortcut_url_spec);
 
+  // Deletes all of the ShortcutsProvider::Shortcuts.
+  bool DeleteAllShortcuts();
+
   // Loads all of the shortcuts.
   bool LoadShortcuts(
       std::map<std::string, shortcuts_provider::Shortcut>* shortcuts);
 
  private:
+  // Ensures that the table is present.
+  bool EnsureTable();
+
   friend class ShortcutsDatabaseTest;
   FRIEND_TEST_ALL_PREFIXES(ShortcutsDatabaseTest, AddShortcut);
   FRIEND_TEST_ALL_PREFIXES(ShortcutsDatabaseTest, UpdateShortcut);
diff --git a/chrome/browser/history/shortcuts_database_unittest.cc b/chrome/browser/history/shortcuts_database_unittest.cc
index 88c802b..216df83 100644
--- a/chrome/browser/history/shortcuts_database_unittest.cc
+++ b/chrome/browser/history/shortcuts_database_unittest.cc
@@ -59,18 +59,18 @@ class ShortcutsDatabaseTest : public testing::Test {
   void AddAll();
 
   ScopedTempDir temp_dir_;
-  scoped_ptr<ShortcutsDatabase> db_;
+  scoped_refptr<ShortcutsDatabase> db_;
 };
 
 void ShortcutsDatabaseTest::SetUp() {
   ASSERT_TRUE(temp_dir_.CreateUniqueTempDir());
-  db_.reset(new ShortcutsDatabase(temp_dir_.path()));
+  db_ = new ShortcutsDatabase(temp_dir_.path());
   ASSERT_TRUE(db_->Init());
   ClearDB();
 }
 
 void ShortcutsDatabaseTest::TearDown() {
-  db_.reset();
+  db_ = NULL;
 }
 
 void ShortcutsDatabaseTest::ClearDB() {
@@ -185,4 +185,14 @@ TEST_F(ShortcutsDatabaseTest, LoadShortcuts) {
   }
 }
 
+TEST_F(ShortcutsDatabaseTest, DeleteAllShortcuts) {
+  AddAll();
+  std::map<std::string, Shortcut> shortcuts;
+  EXPECT_TRUE(db_->LoadShortcuts(&shortcuts));
+  EXPECT_EQ(arraysize(shortcut_test_db), shortcuts.size());
+  EXPECT_TRUE(db_->DeleteAllShortcuts());
+  EXPECT_TRUE(db_->LoadShortcuts(&shortcuts));
+  EXPECT_EQ(0U, shortcuts.size());
+}
+
 }  // namespace history