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

11 files changed, 86 insertions, 87 deletions

diff --git a/chrome/renderer/autofill/password_autofill_agent_browsertest.cc b/chrome/renderer/autofill/password_autofill_agent_browsertest.cc
index 4a619f5..567c305 100644
--- a/chrome/renderer/autofill/password_autofill_agent_browsertest.cc
+++ b/chrome/renderer/autofill/password_autofill_agent_browsertest.cc
@@ -251,7 +251,7 @@ TEST_F(PasswordAutofillAgentTest, NoInitialAutocompleteForReadOnly) {
 
   // Only the username should have been autocompleted.
   // TODO(jcivelli): may be we should not event fill the username?
-  CheckTextFieldsState(kAliceUsername, true, "", false);
+  CheckTextFieldsState(kAliceUsername, true, std::string(), false);
 }
 
 // Tests that having a non-matching username precludes the autocomplete.
@@ -263,7 +263,7 @@ TEST_F(PasswordAutofillAgentTest, NoInitialAutocompleteForFilledField) {
   SimulateOnFillPasswordForm(fill_data_);
 
   // Neither field should be autocompleted.
-  CheckTextFieldsState("bogus", false, "", false);
+  CheckTextFieldsState("bogus", false, std::string(), false);
 }
 
 // Tests that having a matching username does not preclude the autocomplete.
@@ -288,7 +288,7 @@ TEST_F(PasswordAutofillAgentTest, PasswordClearOnEdit) {
   SimulateUsernameChange("alicia", true);
 
   // The password should have been cleared.
-  CheckTextFieldsState("alicia", false, "", false);
+  CheckTextFieldsState("alicia", false, std::string(), false);
 }
 
 // Tests that we only autocomplete on focus lost and with a full username match
@@ -299,27 +299,27 @@ TEST_F(PasswordAutofillAgentTest, WaitUsername) {
   SimulateOnFillPasswordForm(fill_data_);
 
   // No auto-fill should have taken place.
-  CheckTextFieldsState("", false, "", false);
+  CheckTextFieldsState(std::string(), false, std::string(), false);
 
   // No autocomplete should happen when text is entered in the username.
   SimulateUsernameChange("a", true);
-  CheckTextFieldsState("a", false, "", false);
+  CheckTextFieldsState("a", false, std::string(), false);
   SimulateUsernameChange("al", true);
-  CheckTextFieldsState("al", false, "", false);
+  CheckTextFieldsState("al", false, std::string(), false);
   SimulateUsernameChange(kAliceUsername, true);
-  CheckTextFieldsState(kAliceUsername, false, "", false);
+  CheckTextFieldsState(kAliceUsername, false, std::string(), false);
 
   // Autocomplete should happen only when the username textfield is blurred with
   // a full match.
   username_element_.setValue("a");
   autofill_agent_->textFieldDidEndEditing(username_element_);
-  CheckTextFieldsState("a", false, "", false);
+  CheckTextFieldsState("a", false, std::string(), false);
   username_element_.setValue("al");
   autofill_agent_->textFieldDidEndEditing(username_element_);
-  CheckTextFieldsState("al", false, "", false);
+  CheckTextFieldsState("al", false, std::string(), false);
   username_element_.setValue("alices");
   autofill_agent_->textFieldDidEndEditing(username_element_);
-  CheckTextFieldsState("alices", false, "", false);
+  CheckTextFieldsState("alices", false, std::string(), false);
   username_element_.setValue(ASCIIToUTF16(kAliceUsername));
   autofill_agent_->textFieldDidEndEditing(username_element_);
   CheckTextFieldsState(kAliceUsername, true, kAlicePassword, true);
@@ -351,7 +351,7 @@ TEST_F(PasswordAutofillAgentTest, InlineAutocomplete) {
   // Test that deleting does not trigger autocomplete.
   SimulateKeyDownEvent(username_element_, ui::VKEY_BACK);
   SimulateUsernameChange("alic", true);
-  CheckTextFieldsState("alic", false, "", false);
+  CheckTextFieldsState("alic", false, std::string(), false);
   CheckUsernameSelection(4, 4);  // No selection.
   // Reset the last pressed key to something other than backspace.
   SimulateKeyDownEvent(username_element_, ui::VKEY_A);
@@ -361,7 +361,7 @@ TEST_F(PasswordAutofillAgentTest, InlineAutocomplete) {
   // practice the username should no longer be 'alice' and the selected range
   // should be empty.
   SimulateUsernameChange("alf", true);
-  CheckTextFieldsState("alf", false, "", false);
+  CheckTextFieldsState("alf", false, std::string(), false);
   CheckUsernameSelection(3, 3);  // No selection.
 
   // Ok, so now the user removes all the text and enters the letter 'b'.
@@ -379,7 +379,7 @@ TEST_F(PasswordAutofillAgentTest, InlineAutocomplete) {
   // want case-sensitive autocompletion, so the username and the selected range
   // should be empty.
   SimulateUsernameChange("c", true);
-  CheckTextFieldsState("c", false, "", false);
+  CheckTextFieldsState("c", false, std::string(), false);
   CheckUsernameSelection(1, 1);
 }
 
@@ -419,7 +419,7 @@ TEST_F(PasswordAutofillAgentTest, SuggestionSelect) {
                                                WebKit::WebString(),
                                                0);
   // Autocomplete should not have kicked in.
-  CheckTextFieldsState("", false, "", false);
+  CheckTextFieldsState(std::string(), false, std::string(), false);
 }
 
 }  // namespace autofill
diff --git a/chrome/renderer/automation/automation_renderer_helper_browsertest.cc b/chrome/renderer/automation/automation_renderer_helper_browsertest.cc
index 659d312..65bd018 100644
--- a/chrome/renderer/automation/automation_renderer_helper_browsertest.cc
+++ b/chrome/renderer/automation/automation_renderer_helper_browsertest.cc
@@ -84,9 +84,9 @@ TEST_F(AutomationRendererHelperTest, RTLSnapshot) {
 }
 
 TEST_F(AutomationRendererHelperTest, ScriptChain) {
-  ScriptEvaluationRequest request("({'result': 10})", "");
-  ScriptEvaluationRequest request_plus1(
-      "({'result': arguments[0].result + 1})", "");
+  ScriptEvaluationRequest request("({'result': 10})", std::string());
+  ScriptEvaluationRequest request_plus1("({'result': arguments[0].result + 1})",
+                                        std::string());
   std::vector<ScriptEvaluationRequest> script_chain;
   script_chain.push_back(request);
   script_chain.push_back(request_plus1);
@@ -102,10 +102,10 @@ TEST_F(AutomationRendererHelperTest, ScriptChain) {
 }
 
 TEST_F(AutomationRendererHelperTest, ScriptChainError) {
-  ScriptEvaluationRequest request("({'result': 10})", "");
+  ScriptEvaluationRequest request("({'result': 10})", std::string());
   ScriptEvaluationRequest error_request(
       "({'result': arguments[0].result + 1, 'error': {'msg': 'some msg'}})",
-      "");
+      std::string());
   std::vector<ScriptEvaluationRequest> script_chain;
   script_chain.push_back(request);
   script_chain.push_back(error_request);
diff --git a/chrome/renderer/chrome_content_renderer_client_unittest.cc b/chrome/renderer/chrome_content_renderer_client_unittest.cc
index b099eea..1387ff0 100644
--- a/chrome/renderer/chrome_content_renderer_client_unittest.cc
+++ b/chrome/renderer/chrome_content_renderer_client_unittest.cc
@@ -96,8 +96,8 @@ scoped_refptr<const extensions::Extension> CreateTestExtension(
 
 scoped_refptr<const extensions::Extension> CreateExtension(
     bool is_unrestricted, bool is_from_webstore) {
-  return CreateTestExtension(is_unrestricted, is_from_webstore, kNotHostedApp,
-                             "");
+  return CreateTestExtension(
+      is_unrestricted, is_from_webstore, kNotHostedApp, std::string());
 }
 
 scoped_refptr<const extensions::Extension> CreateHostedApp(
diff --git a/chrome/renderer/content_settings_observer_browsertest.cc b/chrome/renderer/content_settings_observer_browsertest.cc
index f4777d2..8397c94 100644
--- a/chrome/renderer/content_settings_observer_browsertest.cc
+++ b/chrome/renderer/content_settings_observer_browsertest.cc
@@ -110,12 +110,11 @@ TEST_F(ChromeRenderViewTest, JSBlockSentAfterPageLoad) {
   ContentSettingsForOneType& script_setting_rules =
       content_setting_rules.script_rules;
   script_setting_rules.push_back(
-      ContentSettingPatternSource(
-          ContentSettingsPattern::Wildcard(),
-          ContentSettingsPattern::Wildcard(),
-          CONTENT_SETTING_BLOCK,
-          "",
-          false));
+      ContentSettingPatternSource(ContentSettingsPattern::Wildcard(),
+                                  ContentSettingsPattern::Wildcard(),
+                                  CONTENT_SETTING_BLOCK,
+                                  std::string(),
+                                  false));
   ContentSettingsObserver* observer = ContentSettingsObserver::Get(view_);
   observer->SetContentSettingRules(&content_setting_rules);
 
@@ -193,7 +192,7 @@ TEST_F(ChromeRenderViewTest, ImagesBlockedByDefault) {
       ContentSettingPatternSource(ContentSettingsPattern::Wildcard(),
                                   ContentSettingsPattern::Wildcard(),
                                   CONTENT_SETTING_BLOCK,
-                                  "",
+                                  std::string(),
                                   false));
 
   ContentSettingsObserver* observer = ContentSettingsObserver::Get(view_);
@@ -211,7 +210,7 @@ TEST_F(ChromeRenderViewTest, ImagesBlockedByDefault) {
           ContentSettingsPattern::Wildcard(),
           ContentSettingsPattern::FromString(mock_observer.image_origin_),
           CONTENT_SETTING_ALLOW,
-          "",
+          std::string(),
           false));
 
   EXPECT_CALL(
@@ -236,7 +235,7 @@ TEST_F(ChromeRenderViewTest, ImagesAllowedByDefault) {
       ContentSettingPatternSource(ContentSettingsPattern::Wildcard(),
                                   ContentSettingsPattern::Wildcard(),
                                   CONTENT_SETTING_ALLOW,
-                                  "",
+                                  std::string(),
                                   false));
 
   ContentSettingsObserver* observer = ContentSettingsObserver::Get(view_);
@@ -255,7 +254,7 @@ TEST_F(ChromeRenderViewTest, ImagesAllowedByDefault) {
           ContentSettingsPattern::Wildcard(),
           ContentSettingsPattern::FromString(mock_observer.image_origin_),
           CONTENT_SETTING_BLOCK,
-          "",
+          std::string(),
           false));
   EXPECT_CALL(mock_observer,
               OnContentBlocked(CONTENT_SETTINGS_TYPE_IMAGES, std::string()));
@@ -270,12 +269,11 @@ TEST_F(ChromeRenderViewTest, ContentSettingsBlockScripts) {
   ContentSettingsForOneType& script_setting_rules =
       content_setting_rules.script_rules;
   script_setting_rules.push_back(
-      ContentSettingPatternSource(
-          ContentSettingsPattern::Wildcard(),
-          ContentSettingsPattern::Wildcard(),
-          CONTENT_SETTING_BLOCK,
-          "",
-          false));
+      ContentSettingPatternSource(ContentSettingsPattern::Wildcard(),
+                                  ContentSettingsPattern::Wildcard(),
+                                  CONTENT_SETTING_BLOCK,
+                                  std::string(),
+                                  false));
 
   ContentSettingsObserver* observer = ContentSettingsObserver::Get(view_);
   observer->SetContentSettingRules(&content_setting_rules);
@@ -306,12 +304,11 @@ TEST_F(ChromeRenderViewTest, ContentSettingsAllowScripts) {
   ContentSettingsForOneType& script_setting_rules =
       content_setting_rules.script_rules;
   script_setting_rules.push_back(
-      ContentSettingPatternSource(
-          ContentSettingsPattern::Wildcard(),
-          ContentSettingsPattern::Wildcard(),
-          CONTENT_SETTING_ALLOW,
-          "",
-          false));
+      ContentSettingPatternSource(ContentSettingsPattern::Wildcard(),
+                                  ContentSettingsPattern::Wildcard(),
+                                  CONTENT_SETTING_ALLOW,
+                                  std::string(),
+                                  false));
 
   ContentSettingsObserver* observer = ContentSettingsObserver::Get(view_);
   observer->SetContentSettingRules(&content_setting_rules);
@@ -343,18 +340,20 @@ TEST_F(ChromeRenderViewTest, ContentSettingsInterstitialPages) {
   ContentSettingsForOneType& script_setting_rules =
       content_setting_rules.script_rules;
   script_setting_rules.push_back(
-      ContentSettingPatternSource(
-          ContentSettingsPattern::Wildcard(),
-          ContentSettingsPattern::Wildcard(),
-          CONTENT_SETTING_BLOCK, "", false));
+      ContentSettingPatternSource(ContentSettingsPattern::Wildcard(),
+                                  ContentSettingsPattern::Wildcard(),
+                                  CONTENT_SETTING_BLOCK,
+                                  std::string(),
+                                  false));
   // Block images.
   ContentSettingsForOneType& image_setting_rules =
       content_setting_rules.image_rules;
   image_setting_rules.push_back(
-      ContentSettingPatternSource(
-          ContentSettingsPattern::Wildcard(),
-          ContentSettingsPattern::Wildcard(),
-          CONTENT_SETTING_BLOCK, "", false));
+      ContentSettingPatternSource(ContentSettingsPattern::Wildcard(),
+                                  ContentSettingsPattern::Wildcard(),
+                                  CONTENT_SETTING_BLOCK,
+                                  std::string(),
+                                  false));
 
   ContentSettingsObserver* observer = ContentSettingsObserver::Get(view_);
   observer->SetContentSettingRules(&content_setting_rules);
diff --git a/chrome/renderer/extensions/chrome_v8_context.cc b/chrome/renderer/extensions/chrome_v8_context.cc
index b4ae80e..5feff00 100644
--- a/chrome/renderer/extensions/chrome_v8_context.cc
+++ b/chrome/renderer/extensions/chrome_v8_context.cc
@@ -63,7 +63,7 @@ void ChromeV8Context::Invalidate() {
 }
 
 std::string ChromeV8Context::GetExtensionID() {
-  return extension_ ? extension_->id() : "";
+  return extension_ ? extension_->id() : std::string();
 }
 
 // static
@@ -187,7 +187,7 @@ std::string ChromeV8Context::GetContextTypeDescription() {
     case Feature::WEB_PAGE_CONTEXT:            return "WEB_PAGE";
   }
   NOTREACHED();
-  return "";
+  return std::string();
 }
 
 ChromeV8Context* ChromeV8Context::GetContext() {
diff --git a/chrome/renderer/extensions/extension_helper.cc b/chrome/renderer/extensions/extension_helper.cc
index a488cb7..ac456a8 100644
--- a/chrome/renderer/extensions/extension_helper.cc
+++ b/chrome/renderer/extensions/extension_helper.cc
@@ -313,8 +313,12 @@ void ExtensionHelper::OnExecuteCode(
   WebFrame* main_frame = webview->mainFrame();
   if (!main_frame) {
     ListValue val;
-    Send(new ExtensionHostMsg_ExecuteCodeFinished(
-        routing_id(), params.request_id, "No main frame", -1, GURL(""), val));
+    Send(new ExtensionHostMsg_ExecuteCodeFinished(routing_id(),
+                                                  params.request_id,
+                                                  "No main frame",
+                                                  -1,
+                                                  GURL(std::string()),
+                                                  val));
     return;
   }
 
diff --git a/chrome/renderer/extensions/resource_request_policy.cc b/chrome/renderer/extensions/resource_request_policy.cc
index 116b218..83ccb3f 100644
--- a/chrome/renderer/extensions/resource_request_policy.cc
+++ b/chrome/renderer/extensions/resource_request_policy.cc
@@ -51,7 +51,8 @@ bool ResourceRequestPolicy::CanRequestResource(
   // some extensions want to be able to do things like create their own
   // launchers.
   std::string resource_root_relative_path =
-      resource_url.path().empty() ? "" : resource_url.path().substr(1);
+      resource_url.path().empty() ? std::string()
+                                  : resource_url.path().substr(1);
   if (extension->is_hosted_app() &&
       !IconsInfo::GetIcons(extension)
           .ContainsPath(resource_root_relative_path)) {
diff --git a/chrome/renderer/extensions/user_script_scheduler.cc b/chrome/renderer/extensions/user_script_scheduler.cc
index 3cb01ba..f194a23 100644
--- a/chrome/renderer/extensions/user_script_scheduler.cc
+++ b/chrome/renderer/extensions/user_script_scheduler.cc
@@ -147,13 +147,13 @@ void UserScriptScheduler::ExecuteCodeImpl(
   // Since extension info is sent separately from user script info, they can
   // be out of sync. We just ignore this situation.
   if (!extension) {
-    render_view->Send(new ExtensionHostMsg_ExecuteCodeFinished(
-        render_view->GetRoutingID(),
-        params.request_id,
-        "",  // no error
-        -1,
-        GURL(""),
-        execution_results));
+    render_view->Send(
+        new ExtensionHostMsg_ExecuteCodeFinished(render_view->GetRoutingID(),
+                                                 params.request_id,
+                                                 std::string(),  // no error
+                                                 -1,
+                                                 GURL(std::string()),
+                                                 execution_results));
     return;
   }
 
diff --git a/chrome/renderer/extensions/user_script_slave.cc b/chrome/renderer/extensions/user_script_slave.cc
index f715207..3e64b7d 100644
--- a/chrome/renderer/extensions/user_script_slave.cc
+++ b/chrome/renderer/extensions/user_script_slave.cc
@@ -92,7 +92,7 @@ std::string UserScriptSlave::GetExtensionIdForIsolatedWorld(
     if (iter->second == isolated_world_id)
       return iter->first;
   }
-  return "";
+  return std::string();
 }
 
 // static
diff --git a/chrome/renderer/plugins/plugin_uma_unittest.cc b/chrome/renderer/plugins/plugin_uma_unittest.cc
index 99e6271..3b1950c 100644
--- a/chrome/renderer/plugins/plugin_uma_unittest.cc
+++ b/chrome/renderer/plugins/plugin_uma_unittest.cc
@@ -118,9 +118,8 @@ TEST_F(PluginUMATest, WidevineCdm) {
 }
 
 TEST_F(PluginUMATest, BySrcExtension) {
-  ExpectPluginType(PluginUMAReporter::QUICKTIME,
-                   "",
-                   GURL("file://file.mov"));
+  ExpectPluginType(
+      PluginUMAReporter::QUICKTIME, std::string(), GURL("file://file.mov"));
 
   // When plugin's mime type is given, we don't check extension.
   ExpectPluginType(PluginUMAReporter::UNSUPPORTED_MIMETYPE,
@@ -128,40 +127,36 @@ TEST_F(PluginUMATest, BySrcExtension) {
                    GURL("http://file.mov"));
 
   ExpectPluginType(PluginUMAReporter::WINDOWS_MEDIA_PLAYER,
-                   "",
+                   std::string(),
                    GURL("file://file.asx"));
-  ExpectPluginType(PluginUMAReporter::REALPLAYER,
-                   "",
-                   GURL("file://file.rm"));
+  ExpectPluginType(
+      PluginUMAReporter::REALPLAYER, std::string(), GURL("file://file.rm"));
   ExpectPluginType(PluginUMAReporter::QUICKTIME,
-                   "",
+                   std::string(),
                    GURL("http://aaa/file.mov?x=aaaa&y=b#c"));
   ExpectPluginType(PluginUMAReporter::QUICKTIME,
-                   "",
+                   std::string(),
                    GURL("http://file.mov?x=aaaa&y=b#c"));
   ExpectPluginType(PluginUMAReporter::SHOCKWAVE_FLASH,
-                   "",
+                   std::string(),
                    GURL("http://file.swf?x=aaaa&y=b#c"));
   ExpectPluginType(PluginUMAReporter::SHOCKWAVE_FLASH,
-                   "",
+                   std::string(),
                    GURL("http://file.spl?x=aaaa&y=b#c"));
 
   ExpectPluginType(PluginUMAReporter::UNSUPPORTED_EXTENSION,
-                   "",
+                   std::string(),
                    GURL("http://file.unknown_extension"));
-  ExpectPluginType(PluginUMAReporter::UNSUPPORTED_EXTENSION,
-                   "",
-                   GURL("http://"));
-  ExpectPluginType(PluginUMAReporter::UNSUPPORTED_EXTENSION,
-                   "",
-                   GURL("mov"));
+  ExpectPluginType(
+      PluginUMAReporter::UNSUPPORTED_EXTENSION, std::string(), GURL("http://"));
+  ExpectPluginType(
+      PluginUMAReporter::UNSUPPORTED_EXTENSION, std::string(), GURL("mov"));
 }
 
 TEST_F(PluginUMATest, CaseSensitivity) {
   ExpectPluginType(PluginUMAReporter::QUICKTIME,
                    "video/QUICKTIME",
                    GURL("http://file.aaa"));
-  ExpectPluginType(PluginUMAReporter::QUICKTIME,
-                   "",
-                   GURL("http://file.MoV"));
+  ExpectPluginType(
+      PluginUMAReporter::QUICKTIME, std::string(), GURL("http://file.MoV"));
 }
diff --git a/chrome/renderer/safe_browsing/malware_dom_details_browsertest.cc b/chrome/renderer/safe_browsing/malware_dom_details_browsertest.cc
index 034655f..8a120cb 100644
--- a/chrome/renderer/safe_browsing/malware_dom_details_browsertest.cc
+++ b/chrome/renderer/safe_browsing/malware_dom_details_browsertest.cc
@@ -97,7 +97,7 @@ TEST_F(MalwareDOMDetailsTest, Everything) {
   }
 
   { // >50 subframes, to verify kMaxNodes.
-    std::string html = "";
+    std::string html;
     for (int i = 0; i < 55; ++i) {
       // The iframe contents is just a number.
       GURL iframe_url(base::StringPrintf("%s%d", urlprefix, i));
@@ -113,7 +113,7 @@ TEST_F(MalwareDOMDetailsTest, Everything) {
   }
 
   { // A page with >50 scripts, to verify kMaxNodes.
-    std::string html = "";
+    std::string html;
     for (int i = 0; i < 55; ++i) {
       // The iframe contents is just a number.
       GURL script_url(base::StringPrintf("%s%d", urlprefix, i));