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

4 files changed, 34 insertions, 16 deletions

diff --git a/chrome/browser/prefs/command_line_pref_store_unittest.cc b/chrome/browser/prefs/command_line_pref_store_unittest.cc
index 5d2c939..1e23383 100644
--- a/chrome/browser/prefs/command_line_pref_store_unittest.cc
+++ b/chrome/browser/prefs/command_line_pref_store_unittest.cc
@@ -116,7 +116,7 @@ TEST(CommandLinePrefStoreTest, MultipleSwitches) {
   ASSERT_EQ(Value::TYPE_DICTIONARY, value->GetType());
   ProxyConfigDictionary dict(static_cast<const DictionaryValue*>(value));
 
-  std::string string_result = "";
+  std::string string_result;
 
   ASSERT_TRUE(dict.GetProxyServer(&string_result));
   EXPECT_EQ("proxy", string_result);
@@ -172,9 +172,9 @@ TEST(CommandLinePrefStoreTest, ManualProxyModeInference) {
   store2->VerifyProxyMode(ProxyPrefs::MODE_PAC_SCRIPT);
 
   CommandLine cl3(CommandLine::NO_PROGRAM);
-  cl3.AppendSwitchASCII(switches::kProxyServer, "");
+  cl3.AppendSwitchASCII(switches::kProxyServer, std::string());
   scoped_refptr<TestCommandLinePrefStore> store3 =
-        new TestCommandLinePrefStore(&cl3);
+      new TestCommandLinePrefStore(&cl3);
   store3->VerifyProxyMode(ProxyPrefs::MODE_DIRECT);
 }
 
diff --git a/chrome/browser/prefs/proxy_config_dictionary.cc b/chrome/browser/prefs/proxy_config_dictionary.cc
index a99fa7c..b6db822 100644
--- a/chrome/browser/prefs/proxy_config_dictionary.cc
+++ b/chrome/browser/prefs/proxy_config_dictionary.cc
@@ -67,12 +67,20 @@ bool ProxyConfigDictionary::HasBypassList() const {
 
 // static
 DictionaryValue* ProxyConfigDictionary::CreateDirect() {
-  return CreateDictionary(ProxyPrefs::MODE_DIRECT, "", false, "", "");
+  return CreateDictionary(ProxyPrefs::MODE_DIRECT,
+                          std::string(),
+                          false,
+                          std::string(),
+                          std::string());
 }
 
 // static
 DictionaryValue* ProxyConfigDictionary::CreateAutoDetect() {
-  return CreateDictionary(ProxyPrefs::MODE_AUTO_DETECT, "", false, "", "");
+  return CreateDictionary(ProxyPrefs::MODE_AUTO_DETECT,
+                          std::string(),
+                          false,
+                          std::string(),
+                          std::string());
 }
 
 // static
@@ -80,7 +88,10 @@ DictionaryValue* ProxyConfigDictionary::CreatePacScript(
     const std::string& pac_url,
     bool pac_mandatory) {
   return CreateDictionary(ProxyPrefs::MODE_PAC_SCRIPT,
-                          pac_url, pac_mandatory, "", "");
+                          pac_url,
+                          pac_mandatory,
+                          std::string(),
+                          std::string());
 }
 
 // static
@@ -88,8 +99,11 @@ DictionaryValue* ProxyConfigDictionary::CreateFixedServers(
     const std::string& proxy_server,
     const std::string& bypass_list) {
   if (!proxy_server.empty()) {
-    return CreateDictionary(
-        ProxyPrefs::MODE_FIXED_SERVERS, "", false, proxy_server, bypass_list);
+    return CreateDictionary(ProxyPrefs::MODE_FIXED_SERVERS,
+                            std::string(),
+                            false,
+                            proxy_server,
+                            bypass_list);
   } else {
     return CreateDirect();
   }
@@ -97,7 +111,11 @@ DictionaryValue* ProxyConfigDictionary::CreateFixedServers(
 
 // static
 DictionaryValue* ProxyConfigDictionary::CreateSystem() {
-  return CreateDictionary(ProxyPrefs::MODE_SYSTEM, "", false, "", "");
+  return CreateDictionary(ProxyPrefs::MODE_SYSTEM,
+                          std::string(),
+                          false,
+                          std::string(),
+                          std::string());
 }
 
 // static
diff --git a/chrome/browser/prefs/proxy_policy_unittest.cc b/chrome/browser/prefs/proxy_policy_unittest.cc
index ec51894..512e514 100644
--- a/chrome/browser/prefs/proxy_policy_unittest.cc
+++ b/chrome/browser/prefs/proxy_policy_unittest.cc
@@ -68,9 +68,9 @@ void assertBypassList(const ProxyConfigDictionary& dict,
 void assertProxyModeWithoutParams(const ProxyConfigDictionary& dict,
                                   ProxyPrefs::ProxyMode proxy_mode) {
   assertProxyMode(dict, proxy_mode);
-  assertProxyServer(dict, "");
-  assertPacUrl(dict, "");
-  assertBypassList(dict, "");
+  assertProxyServer(dict, std::string());
+  assertPacUrl(dict, std::string());
+  assertBypassList(dict, std::string());
 }
 
 }  // namespace
@@ -130,7 +130,7 @@ TEST_F(ProxyPolicyTest, OverridesCommandLineOptions) {
   ProxyConfigDictionary dict(prefs->GetDictionary(prefs::kProxy));
   assertProxyMode(dict, ProxyPrefs::MODE_FIXED_SERVERS);
   assertProxyServer(dict, "789");
-  assertPacUrl(dict, "");
+  assertPacUrl(dict, std::string());
   assertBypassList(dict, "123");
 
   // Try a second time time with the managed PrefStore in place, the
@@ -140,7 +140,7 @@ TEST_F(ProxyPolicyTest, OverridesCommandLineOptions) {
   ProxyConfigDictionary dict2(prefs->GetDictionary(prefs::kProxy));
   assertProxyMode(dict2, ProxyPrefs::MODE_FIXED_SERVERS);
   assertProxyServer(dict2, "ghi");
-  assertPacUrl(dict2, "");
+  assertPacUrl(dict2, std::string());
   assertBypassList(dict2, "abc");
 }
 
@@ -160,7 +160,7 @@ TEST_F(ProxyPolicyTest, OverridesUnrelatedCommandLineOptions) {
   ProxyConfigDictionary dict(prefs->GetDictionary(prefs::kProxy));
   assertProxyMode(dict, ProxyPrefs::MODE_FIXED_SERVERS);
   assertProxyServer(dict, "789");
-  assertPacUrl(dict, "");
+  assertPacUrl(dict, std::string());
   assertBypassList(dict, "123");
 
   // Try a second time time with the managed PrefStore in place, the
diff --git a/chrome/browser/prefs/session_startup_pref.cc b/chrome/browser/prefs/session_startup_pref.cc
index d822cc0..fbbf62f 100644
--- a/chrome/browser/prefs/session_startup_pref.cc
+++ b/chrome/browser/prefs/session_startup_pref.cc
@@ -45,7 +45,7 @@ void URLListToPref(const base::ListValue* url_list, SessionStartupPref* pref) {
   for (size_t i = 0; i < url_list->GetSize(); ++i) {
     std::string url_text;
     if (url_list->GetString(i, &url_text)) {
-      GURL fixed_url = URLFixerUpper::FixupURL(url_text, "");
+      GURL fixed_url = URLFixerUpper::FixupURL(url_text, std::string());
       pref->urls.push_back(fixed_url);
     }
   }