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

5 files changed, 10 insertions, 10 deletions

diff --git a/dbus/end_to_end_async_unittest.cc b/dbus/end_to_end_async_unittest.cc
index 0a3446e..6943494 100644
--- a/dbus/end_to_end_async_unittest.cc
+++ b/dbus/end_to_end_async_unittest.cc
@@ -185,7 +185,7 @@ class EndToEndAsyncTest : public testing::Test {
       ASSERT_TRUE(reader.PopString(&response_string));
       response_strings_.push_back(response_string);
     } else {
-      response_strings_.push_back("");
+      response_strings_.push_back(std::string());
     }
     message_loop_.Quit();
   };
@@ -205,7 +205,7 @@ class EndToEndAsyncTest : public testing::Test {
       ASSERT_NE("", error->GetErrorName());
       error_names_.push_back(error->GetErrorName());
     } else {
-      error_names_.push_back("");
+      error_names_.push_back(std::string());
     }
     message_loop_.Quit();
   }
diff --git a/dbus/message.cc b/dbus/message.cc
index ce53a48..737b0c4 100644
--- a/dbus/message.cc
+++ b/dbus/message.cc
@@ -87,7 +87,7 @@ std::string Message::GetMessageTypeAsString() {
       return "MESSAGE_ERROR";
   }
   NOTREACHED();
-  return "";
+  return std::string();
 }
 
 std::string Message::ToStringInternal(const std::string& indent,
@@ -251,7 +251,7 @@ std::string Message::ToStringInternal(const std::string& indent,
 // ...
 std::string Message::ToString() {
   if (!raw_message_)
-    return "";
+    return std::string();
 
   // Generate headers first.
   std::string headers;
@@ -268,7 +268,7 @@ std::string Message::ToString() {
 
   // Generate the payload.
   MessageReader reader(this);
-  return headers + "\n" + ToStringInternal("", &reader);
+  return headers + "\n" + ToStringInternal(std::string(), &reader);
 }
 
 bool Message::SetDestination(const std::string& destination) {
diff --git a/dbus/message_unittest.cc b/dbus/message_unittest.cc
index 7e4455a8..383e1c1 100644
--- a/dbus/message_unittest.cc
+++ b/dbus/message_unittest.cc
@@ -557,7 +557,7 @@ TEST(MessageTest, GetAndSetHeaders) {
   scoped_ptr<dbus::Response> message(dbus::Response::CreateEmpty());
 
   EXPECT_EQ("", message->GetDestination());
-  EXPECT_EQ(dbus::ObjectPath(""), message->GetPath());
+  EXPECT_EQ(dbus::ObjectPath(std::string()), message->GetPath());
   EXPECT_EQ("", message->GetInterface());
   EXPECT_EQ("", message->GetMember());
   EXPECT_EQ("", message->GetErrorName());
@@ -587,7 +587,7 @@ TEST(MessageTest, GetAndSetHeaders) {
 TEST(MessageTest, SetInvalidHeaders) {
   scoped_ptr<dbus::Response> message(dbus::Response::CreateEmpty());
   EXPECT_EQ("", message->GetDestination());
-  EXPECT_EQ(dbus::ObjectPath(""), message->GetPath());
+  EXPECT_EQ(dbus::ObjectPath(std::string()), message->GetPath());
   EXPECT_EQ("", message->GetInterface());
   EXPECT_EQ("", message->GetMember());
   EXPECT_EQ("", message->GetErrorName());
@@ -607,7 +607,7 @@ TEST(MessageTest, SetInvalidHeaders) {
   EXPECT_FALSE(message->SetSender("?!#*"));
 
   EXPECT_EQ("", message->GetDestination());
-  EXPECT_EQ(dbus::ObjectPath(""), message->GetPath());
+  EXPECT_EQ(dbus::ObjectPath(std::string()), message->GetPath());
   EXPECT_EQ("", message->GetInterface());
   EXPECT_EQ("", message->GetMember());
   EXPECT_EQ("", message->GetErrorName());
diff --git a/dbus/string_util_unittest.cc b/dbus/string_util_unittest.cc
index 76bdfcb..99eb691 100644
--- a/dbus/string_util_unittest.cc
+++ b/dbus/string_util_unittest.cc
@@ -10,7 +10,7 @@ TEST(StringUtilTest, IsValidObjectPath) {
   EXPECT_TRUE(dbus::IsValidObjectPath("/foo/bar"));
   EXPECT_TRUE(dbus::IsValidObjectPath("/hoge_fuga/piyo123"));
   // Empty string.
-  EXPECT_FALSE(dbus::IsValidObjectPath(""));
+  EXPECT_FALSE(dbus::IsValidObjectPath(std::string()));
   // Emptyr elemnt.
   EXPECT_FALSE(dbus::IsValidObjectPath("//"));
   EXPECT_FALSE(dbus::IsValidObjectPath("/foo//bar"));
diff --git a/dbus/values_util.cc b/dbus/values_util.cc
index 2e2d8e3..7574f39 100644
--- a/dbus/values_util.cc
+++ b/dbus/values_util.cc
@@ -79,7 +79,7 @@ std::string GetTypeSignature(const base::Value& value) {
       return "a{sv}";
     default:
       DLOG(ERROR) << "Unexpected type " << value.GetType();
-      return "";
+      return std::string();
   }
 }