Rewrite std::string("") to std::string(), Linux edition.

This patch was generated by running the empty_string clang tool
across the Chromium Linux compilation database. Implicitly or
explicitly constructing std::string() with a "" argument is
inefficient as the caller needs to emit extra instructions to
pass an argument, and the constructor needlessly copies a byte
into internal storage. Rewriting these instances to simply call
the default constructor appears to save ~14-18 kilobytes on an
optimized release build.

BUG=none

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=193020

Review URL: https://codereview.chromium.org/13145003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@193040 0039d316-1c4b-4281-b951-d872f2087c98

8 files changed, 57 insertions, 52 deletions

diff --git a/chrome/browser/signin/about_signin_internals.cc b/chrome/browser/signin/about_signin_internals.cc
index ad83b0d..e58a013 100644
--- a/chrome/browser/signin/about_signin_internals.cc
+++ b/chrome/browser/signin/about_signin_internals.cc
@@ -25,7 +25,8 @@ AboutSigninInternals::AboutSigninInternals() : profile_(NULL) {
   for (size_t i = 0; i < kNumTokenPrefs; ++i) {
     signin_status_.token_info_map.insert(std::pair<std::string, TokenInfo>(
         kTokenPrefsArray[i],
-        TokenInfo("", "Not Loaded", "", kTokenPrefsArray[i])));
+        TokenInfo(
+            std::string(), "Not Loaded", std::string(), kTokenPrefsArray[i])));
   }
 }
 
@@ -170,7 +171,7 @@ void AboutSigninInternals::NotifyTokenReceivedFailure(
   const std::string value_pref = TokenPrefPath(token_name) + ".value";
   const std::string time_pref = TokenPrefPath(token_name) + ".time";
   const std::string status_pref = TokenPrefPath(token_name) + ".status";
-  profile_->GetPrefs()->SetString(value_pref.c_str(), "");
+  profile_->GetPrefs()->SetString(value_pref.c_str(), std::string());
   profile_->GetPrefs()->SetString(time_pref.c_str(), time_as_str);
   profile_->GetPrefs()->SetString(status_pref.c_str(), error);
 
@@ -186,7 +187,7 @@ void AboutSigninInternals::NotifyClearStoredToken(
   signin_status_.token_info_map[token_name].token.clear();
 
   const std::string value_pref = TokenPrefPath(token_name) + ".value";
-  profile_->GetPrefs()->SetString(value_pref.c_str(), "");
+  profile_->GetPrefs()->SetString(value_pref.c_str(), std::string());
 
   NotifyObservers();
 }
diff --git a/chrome/browser/signin/about_signin_internals_factory.cc b/chrome/browser/signin/about_signin_internals_factory.cc
index ccce353..f5f197f 100644
--- a/chrome/browser/signin/about_signin_internals_factory.cc
+++ b/chrome/browser/signin/about_signin_internals_factory.cc
@@ -42,7 +42,8 @@ void AboutSigninInternalsFactory::RegisterUserPrefs(
   for (int i = UNTIMED_FIELDS_BEGIN; i < UNTIMED_FIELDS_END; ++i) {
     const std::string pref_path = SigninStatusFieldToString(
         static_cast<UntimedSigninStatusField>(i));
-    user_prefs->RegisterStringPref(pref_path.c_str(), "",
+    user_prefs->RegisterStringPref(pref_path.c_str(),
+                                   std::string(),
                                    PrefRegistrySyncable::UNSYNCABLE_PREF);
   }
   for (int i = TIMED_FIELDS_BEGIN; i < TIMED_FIELDS_END; ++i) {
@@ -50,10 +51,10 @@ void AboutSigninInternalsFactory::RegisterUserPrefs(
         static_cast<TimedSigninStatusField>(i)) + ".value";
     const std::string time = SigninStatusFieldToString(
         static_cast<TimedSigninStatusField>(i)) + ".time";
-    user_prefs->RegisterStringPref(value.c_str(), "",
-                                   PrefRegistrySyncable::UNSYNCABLE_PREF);
-    user_prefs->RegisterStringPref(time.c_str(), "",
-                                   PrefRegistrySyncable::UNSYNCABLE_PREF);
+    user_prefs->RegisterStringPref(
+        value.c_str(), std::string(), PrefRegistrySyncable::UNSYNCABLE_PREF);
+    user_prefs->RegisterStringPref(
+        time.c_str(), std::string(), PrefRegistrySyncable::UNSYNCABLE_PREF);
   }
   // TokenService information for about:signin-internals.
   for (size_t i = 0; i < kNumTokenPrefs; i++) {
@@ -61,12 +62,12 @@ void AboutSigninInternalsFactory::RegisterUserPrefs(
     const std::string value = pref + ".value";
     const std::string status = pref + ".status";
     const std::string time = pref + ".time";
-    user_prefs->RegisterStringPref(value.c_str(), "",
-                                   PrefRegistrySyncable::UNSYNCABLE_PREF);
-    user_prefs->RegisterStringPref(status.c_str(), "",
-                                   PrefRegistrySyncable::UNSYNCABLE_PREF);
-    user_prefs->RegisterStringPref(time.c_str(), "",
-                                   PrefRegistrySyncable::UNSYNCABLE_PREF);
+    user_prefs->RegisterStringPref(
+        value.c_str(), std::string(), PrefRegistrySyncable::UNSYNCABLE_PREF);
+    user_prefs->RegisterStringPref(
+        status.c_str(), std::string(), PrefRegistrySyncable::UNSYNCABLE_PREF);
+    user_prefs->RegisterStringPref(
+        time.c_str(), std::string(), PrefRegistrySyncable::UNSYNCABLE_PREF);
   }
 }
 
diff --git a/chrome/browser/signin/oauth2_token_service_unittest.cc b/chrome/browser/signin/oauth2_token_service_unittest.cc
index 3649374..7095b43 100644
--- a/chrome/browser/signin/oauth2_token_service_unittest.cc
+++ b/chrome/browser/signin/oauth2_token_service_unittest.cc
@@ -138,7 +138,7 @@ TEST_F(OAuth2TokenServiceTest, FailureShouldNotRetry) {
   net::TestURLFetcher* fetcher = factory_.GetFetcherByID(0);
   EXPECT_TRUE(fetcher);
   fetcher->set_response_code(net::HTTP_UNAUTHORIZED);
-  fetcher->SetResponseString("");
+  fetcher->SetResponseString(std::string());
   fetcher->delegate()->OnURLFetchComplete(fetcher);
   EXPECT_EQ(0, consumer_.number_of_correct_tokens_);
   EXPECT_EQ(1, consumer_.number_of_errors_);
@@ -251,7 +251,7 @@ TEST_F(OAuth2TokenServiceTest, SuccessAndExpirationAndFailure) {
   fetcher = factory_.GetFetcherByID(0);
   EXPECT_TRUE(fetcher);
   fetcher->set_response_code(net::HTTP_UNAUTHORIZED);
-  fetcher->SetResponseString("");
+  fetcher->SetResponseString(std::string());
   fetcher->delegate()->OnURLFetchComplete(fetcher);
   EXPECT_EQ(1, consumer_.number_of_correct_tokens_);
   EXPECT_EQ(1, consumer_.number_of_errors_);
@@ -374,7 +374,7 @@ TEST_F(OAuth2TokenServiceTest, SuccessAndSignOutAndRequest) {
 
   // Signs out
   service_->IssueAuthTokenForTest(GaiaConstants::kGaiaOAuth2LoginRefreshToken,
-                                  "");
+                                  std::string());
   service_->EraseTokensFromDB();
 
   request = oauth2_service_->StartRequest(std::set<std::string>(), &consumer_);
@@ -404,7 +404,7 @@ TEST_F(OAuth2TokenServiceTest, SuccessAndSignOutAndSignInAndSuccess) {
 
   // Signs out and signs in
   service_->IssueAuthTokenForTest(GaiaConstants::kGaiaOAuth2LoginRefreshToken,
-                                  "");
+                                  std::string());
   service_->EraseTokensFromDB();
   service_->IssueAuthTokenForTest(GaiaConstants::kGaiaOAuth2LoginRefreshToken,
                                   "refreshToken");
@@ -486,7 +486,7 @@ TEST_F(OAuth2TokenServiceTest, RetryingConsumer) {
   net::TestURLFetcher* fetcher = factory_.GetFetcherByID(0);
   EXPECT_TRUE(fetcher);
   fetcher->set_response_code(net::HTTP_UNAUTHORIZED);
-  fetcher->SetResponseString("");
+  fetcher->SetResponseString(std::string());
   fetcher->delegate()->OnURLFetchComplete(fetcher);
   EXPECT_EQ(0, consumer.number_of_correct_tokens_);
   EXPECT_EQ(1, consumer.number_of_errors_);
@@ -494,7 +494,7 @@ TEST_F(OAuth2TokenServiceTest, RetryingConsumer) {
   fetcher = factory_.GetFetcherByID(0);
   EXPECT_TRUE(fetcher);
   fetcher->set_response_code(net::HTTP_UNAUTHORIZED);
-  fetcher->SetResponseString("");
+  fetcher->SetResponseString(std::string());
   fetcher->delegate()->OnURLFetchComplete(fetcher);
   EXPECT_EQ(0, consumer.number_of_correct_tokens_);
   EXPECT_EQ(2, consumer.number_of_errors_);
diff --git a/chrome/browser/signin/signin_internals_util.cc b/chrome/browser/signin/signin_internals_util.cc
index adae0a1..f187418 100644
--- a/chrome/browser/signin/signin_internals_util.cc
+++ b/chrome/browser/signin/signin_internals_util.cc
@@ -98,11 +98,11 @@ std::string SigninStatusFieldToString(UntimedSigninStatusField field) {
     ENUM_CASE(LSID);
     case UNTIMED_FIELDS_END:
       NOTREACHED();
-      return "";
+      return std::string();
   }
 
   NOTREACHED();
-  return "";
+  return std::string();
 }
 
 std::string SigninStatusFieldToString(TimedSigninStatusField field) {
@@ -113,11 +113,11 @@ std::string SigninStatusFieldToString(TimedSigninStatusField field) {
     ENUM_CASE(GET_USER_INFO_STATUS);
     case TIMED_FIELDS_END:
       NOTREACHED();
-      return "";
+      return std::string();
   }
 
   NOTREACHED();
-  return "";
+  return std::string();
 }
 
 SigninStatus::SigninStatus()
@@ -203,10 +203,10 @@ std::string SigninStatusFieldToLabel(UntimedSigninStatusField field) {
       return "Sid (Hash)";
     case UNTIMED_FIELDS_END:
       NOTREACHED();
-      return "";
+      return std::string();
   }
   NOTREACHED();
-  return "";
+  return std::string();
 }
 
 TimedSigninStatusValue SigninStatusFieldToLabel(
@@ -226,10 +226,10 @@ TimedSigninStatusValue SigninStatusFieldToLabel(
                                     "Last OnGetUserInfo Time");
     case TIMED_FIELDS_END:
       NOTREACHED();
-      return TimedSigninStatusValue("Error", "");
+      return TimedSigninStatusValue("Error", std::string());
   }
   NOTREACHED();
-  return TimedSigninStatusValue("Error", "");
+  return TimedSigninStatusValue("Error", std::string());
 }
 
 } //  namespace
diff --git a/chrome/browser/signin/signin_manager.cc b/chrome/browser/signin/signin_manager.cc
index a8bc081..ab5befc 100644
--- a/chrome/browser/signin/signin_manager.cc
+++ b/chrome/browser/signin/signin_manager.cc
@@ -305,10 +305,9 @@ std::string SigninManager::SigninTypeToString(
   }
 
   NOTREACHED();
-  return "";
+  return std::string();
 }
 
-
 bool SigninManager::PrepareForSignin(SigninType type,
                                      const std::string& username,
                                      const std::string& password) {
@@ -468,7 +467,8 @@ void SigninManager::StartSignInWithOAuth(const std::string& username,
   scopes.push_back(GaiaUrls::GetInstance()->oauth1_login_scope());
   const std::string& locale = g_browser_process->GetApplicationLocale();
 
-  client_login_->StartClientOAuth(username, password, scopes, "", locale);
+  client_login_->StartClientOAuth(
+      username, password, scopes, std::string(), locale);
 
   // Register for token availability.  The signin manager will pre-login the
   // user when the GAIA service token is ready for use.  Only do this if we
@@ -549,10 +549,9 @@ void SigninManager::SignOut() {
   profile_->GetPrefs()->ClearPref(prefs::kGoogleServicesUsername);
 
   // Erase (now) stale information from AboutSigninInternals.
-  NotifyDiagnosticsObservers(USERNAME, "");
-  NotifyDiagnosticsObservers(LSID, "");
-  NotifyDiagnosticsObservers(
-      signin_internals_util::SID, "");
+  NotifyDiagnosticsObservers(USERNAME, std::string());
+  NotifyDiagnosticsObservers(LSID, std::string());
+  NotifyDiagnosticsObservers(signin_internals_util::SID, std::string());
 
   TokenService* token_service = TokenServiceFactory::GetForProfile(profile_);
   content::NotificationService::current()->Notify(
diff --git a/chrome/browser/signin/signin_manager_factory.cc b/chrome/browser/signin/signin_manager_factory.cc
index 67e33c0..11dd5e6 100644
--- a/chrome/browser/signin/signin_manager_factory.cc
+++ b/chrome/browser/signin/signin_manager_factory.cc
@@ -39,9 +39,11 @@ SigninManagerFactory* SigninManagerFactory::GetInstance() {
 }
 
 void SigninManagerFactory::RegisterUserPrefs(PrefRegistrySyncable* registry) {
-  registry->RegisterStringPref(prefs::kGoogleServicesLastUsername, "",
+  registry->RegisterStringPref(prefs::kGoogleServicesLastUsername,
+                               std::string(),
                                PrefRegistrySyncable::UNSYNCABLE_PREF);
-  registry->RegisterStringPref(prefs::kGoogleServicesUsername, "",
+  registry->RegisterStringPref(prefs::kGoogleServicesUsername,
+                               std::string(),
                                PrefRegistrySyncable::UNSYNCABLE_PREF);
   registry->RegisterBooleanPref(prefs::kAutologinEnabled, true,
                                 PrefRegistrySyncable::UNSYNCABLE_PREF);
@@ -54,7 +56,8 @@ void SigninManagerFactory::RegisterUserPrefs(PrefRegistrySyncable* registry) {
 
 // static
 void SigninManagerFactory::RegisterPrefs(PrefRegistrySimple* registry) {
-  registry->RegisterStringPref(prefs::kGoogleServicesUsernamePattern, "");
+  registry->RegisterStringPref(prefs::kGoogleServicesUsernamePattern,
+                               std::string());
 }
 
 ProfileKeyedService* SigninManagerFactory::BuildServiceInstanceFor(
diff --git a/chrome/browser/signin/signin_manager_unittest.cc b/chrome/browser/signin/signin_manager_unittest.cc
index 79964d0..c49f7a1 100644
--- a/chrome/browser/signin/signin_manager_unittest.cc
+++ b/chrome/browser/signin/signin_manager_unittest.cc
@@ -308,7 +308,8 @@ TEST_F(SigninManagerTest, SignInClientLogin) {
   manager_->Initialize(profile_.get());
   EXPECT_TRUE(manager_->GetAuthenticatedUsername().empty());
 
-  manager_->StartSignIn("user@gmail.com", "password", "", "");
+  manager_->StartSignIn(
+      "user@gmail.com", "password", std::string(), std::string());
   EXPECT_TRUE(manager_->GetAuthenticatedUsername().empty());
 
   SimulateValidResponseClientLogin(true);
@@ -340,7 +341,7 @@ TEST_F(SigninManagerTest, Prohibited) {
   EXPECT_TRUE(manager_->IsAllowedUsername("happy@google.com"));
   EXPECT_FALSE(manager_->IsAllowedUsername("test@invalid.com"));
   EXPECT_FALSE(manager_->IsAllowedUsername("test@notgoogle.com"));
-  EXPECT_FALSE(manager_->IsAllowedUsername(""));
+  EXPECT_FALSE(manager_->IsAllowedUsername(std::string()));
 }
 
 TEST_F(SigninManagerTest, TestAlternateWildcard) {
@@ -353,7 +354,7 @@ TEST_F(SigninManagerTest, TestAlternateWildcard) {
   EXPECT_TRUE(manager_->IsAllowedUsername("happy@google.com"));
   EXPECT_FALSE(manager_->IsAllowedUsername("test@invalid.com"));
   EXPECT_FALSE(manager_->IsAllowedUsername("test@notgoogle.com"));
-  EXPECT_FALSE(manager_->IsAllowedUsername(""));
+  EXPECT_FALSE(manager_->IsAllowedUsername(std::string()));
 }
 
 TEST_F(SigninManagerTest, ProhibitedAtStartup) {
@@ -421,7 +422,7 @@ TEST_F(SigninManagerTest, SignInWithCredentialsEmptyPasswordValidCookie) {
         net::CookieMonster::SetCookiesCallback());
 
   // Since the password is empty, will verify the gaia cookies first.
-  manager_->StartSignInWithCredentials("0", "user@gmail.com", "");
+  manager_->StartSignInWithCredentials("0", "user@gmail.com", std::string());
 
   WaitUntilUIDone();
 
@@ -434,7 +435,7 @@ TEST_F(SigninManagerTest, SignInWithCredentialsEmptyPasswordNoValidCookie) {
   EXPECT_TRUE(manager_->GetAuthenticatedUsername().empty());
 
   // Since the password is empty, will verify the gaia cookies first.
-  manager_->StartSignInWithCredentials("0", "user@gmail.com", "");
+  manager_->StartSignInWithCredentials("0", "user@gmail.com", std::string());
 
   WaitUntilUIDone();
 
@@ -458,7 +459,7 @@ TEST_F(SigninManagerTest, SignInWithCredentialsEmptyPasswordInValidCookie) {
         net::CookieMonster::SetCookiesCallback());
 
   // Since the password is empty, must verify the gaia cookies first.
-  manager_->StartSignInWithCredentials("0", "user@gmail.com", "");
+  manager_->StartSignInWithCredentials("0", "user@gmail.com", std::string());
 
   WaitUntilUIDone();
 
@@ -471,7 +472,7 @@ TEST_F(SigninManagerTest, SignInClientLoginNoGPlus) {
   manager_->Initialize(profile_.get());
   EXPECT_TRUE(manager_->GetAuthenticatedUsername().empty());
 
-  manager_->StartSignIn("username", "password", "", "");
+  manager_->StartSignIn("username", "password", std::string(), std::string());
   EXPECT_TRUE(manager_->GetAuthenticatedUsername().empty());
 
   SimulateValidResponseClientLogin(false);
@@ -482,7 +483,7 @@ TEST_F(SigninManagerTest, ClearTransientSigninData) {
   manager_->Initialize(profile_.get());
   EXPECT_TRUE(manager_->GetAuthenticatedUsername().empty());
 
-  manager_->StartSignIn("username", "password", "", "");
+  manager_->StartSignIn("username", "password", std::string(), std::string());
   EXPECT_TRUE(manager_->GetAuthenticatedUsername().empty());
 
   SimulateValidResponseClientLogin(false);
@@ -513,7 +514,7 @@ TEST_F(SigninManagerTest, ClearTransientSigninData) {
 
 TEST_F(SigninManagerTest, SignOutClientLogin) {
   manager_->Initialize(profile_.get());
-  manager_->StartSignIn("username", "password", "", "");
+  manager_->StartSignIn("username", "password", std::string(), std::string());
   SimulateValidResponseClientLogin(false);
   manager_->OnClientLoginSuccess(credentials_);
 
@@ -529,7 +530,7 @@ TEST_F(SigninManagerTest, SignOutClientLogin) {
 
 TEST_F(SigninManagerTest, SignInFailureClientLogin) {
   manager_->Initialize(profile_.get());
-  manager_->StartSignIn("username", "password", "", "");
+  manager_->StartSignIn("username", "password", std::string(), std::string());
   GoogleServiceAuthError error(GoogleServiceAuthError::REQUEST_CANCELED);
   manager_->OnClientLoginFailure(error);
 
@@ -547,7 +548,7 @@ TEST_F(SigninManagerTest, SignInFailureClientLogin) {
 
 TEST_F(SigninManagerTest, ProvideSecondFactorSuccess) {
   manager_->Initialize(profile_.get());
-  manager_->StartSignIn("username", "password", "", "");
+  manager_->StartSignIn("username", "password", std::string(), std::string());
   GoogleServiceAuthError error(GoogleServiceAuthError::TWO_FACTOR);
   manager_->OnClientLoginFailure(error);
 
@@ -566,7 +567,7 @@ TEST_F(SigninManagerTest, ProvideSecondFactorSuccess) {
 
 TEST_F(SigninManagerTest, ProvideSecondFactorFailure) {
   manager_->Initialize(profile_.get());
-  manager_->StartSignIn("username", "password", "", "");
+  manager_->StartSignIn("username", "password", std::string(), std::string());
   GoogleServiceAuthError error1(GoogleServiceAuthError::TWO_FACTOR);
   manager_->OnClientLoginFailure(error1);
 
@@ -596,7 +597,7 @@ TEST_F(SigninManagerTest, ProvideSecondFactorFailure) {
 
 TEST_F(SigninManagerTest, SignOutMidConnect) {
   manager_->Initialize(profile_.get());
-  manager_->StartSignIn("username", "password", "", "");
+  manager_->StartSignIn("username", "password", std::string(), std::string());
   manager_->SignOut();
   EXPECT_EQ(0U, google_login_success_.size());
   EXPECT_EQ(0U, google_login_failure_.size());
diff --git a/chrome/browser/signin/token_service_unittest.cc b/chrome/browser/signin/token_service_unittest.cc
index 617a394..fbe83df 100644
--- a/chrome/browser/signin/token_service_unittest.cc
+++ b/chrome/browser/signin/token_service_unittest.cc
@@ -225,7 +225,7 @@ TEST_F(TokenServiceTest, OnTokenSuccessUpdate) {
   EXPECT_EQ(service_->GetTokenForService(GaiaConstants::kSyncService),
             "token2");
 
-  service_->OnIssueAuthTokenSuccess(GaiaConstants::kSyncService, "");
+  service_->OnIssueAuthTokenSuccess(GaiaConstants::kSyncService, std::string());
   EXPECT_TRUE(service_->HasTokenForService(GaiaConstants::kSyncService));
   EXPECT_EQ(service_->GetTokenForService(GaiaConstants::kSyncService), "");
 }