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

6 files changed, 15 insertions, 13 deletions

diff --git a/remoting/protocol/jingle_messages.cc b/remoting/protocol/jingle_messages.cc
index 7d82443..e2408e0 100644
--- a/remoting/protocol/jingle_messages.cc
+++ b/remoting/protocol/jingle_messages.cc
@@ -124,10 +124,9 @@ JingleMessage::NamedCandidate::NamedCandidate(
 
 // static
 bool JingleMessage::IsJingleMessage(const buzz::XmlElement* stanza) {
-  return
-      stanza->Name() == QName(kJabberNamespace, "iq") &&
-      stanza->Attr(QName("", "type")) == "set" &&
-      stanza->FirstNamed(QName(kJingleNamespace, "jingle")) != NULL;
+  return stanza->Name() == QName(kJabberNamespace, "iq") &&
+         stanza->Attr(QName(std::string(), "type")) == "set" &&
+         stanza->FirstNamed(QName(kJingleNamespace, "jingle")) != NULL;
 }
 
 // static
@@ -373,7 +372,7 @@ scoped_ptr<buzz::XmlElement> JingleMessageReply::ToXml(
 
   std::string type;
   std::string error_text;
-  QName name("");
+  QName name;
   switch (error_type) {
     case BAD_REQUEST:
       type = "modify";
diff --git a/remoting/protocol/jingle_session.cc b/remoting/protocol/jingle_session.cc
index c6a4f22..72985c2 100644
--- a/remoting/protocol/jingle_session.cc
+++ b/remoting/protocol/jingle_session.cc
@@ -323,7 +323,8 @@ void JingleSession::OnMessageResponse(
     CloseInternal(SIGNALING_TIMEOUT);
     return;
   } else {
-    const std::string& type = response->Attr(buzz::QName("", "type"));
+    const std::string& type =
+        response->Attr(buzz::QName(std::string(), "type"));
     if (type != "result") {
       LOG(ERROR) << "Received error in response to " << type_str
                  << " message: \"" << response->Str()
@@ -383,7 +384,7 @@ void JingleSession::OnTransportInfoResponse(IqRequest* request,
     return;
   }
 
-  const std::string& type = response->Attr(buzz::QName("", "type"));
+  const std::string& type = response->Attr(buzz::QName(std::string(), "type"));
   if (type != "result") {
     LOG(ERROR) << "Received error in response to transport-info message: \""
                << response->Str() << "\". Terminating the session.";
diff --git a/remoting/protocol/jingle_session_unittest.cc b/remoting/protocol/jingle_session_unittest.cc
index 433356b..76aee23 100644
--- a/remoting/protocol/jingle_session_unittest.cc
+++ b/remoting/protocol/jingle_session_unittest.cc
@@ -323,7 +323,7 @@ TEST_F(JingleSessionTest, Connect) {
       initiate_xml->FirstNamed(buzz::QName(kJingleNamespace, "jingle"));
   ASSERT_TRUE(jingle_element);
   ASSERT_EQ(kClientJid,
-            jingle_element->Attr(buzz::QName("", "initiator")));
+            jingle_element->Attr(buzz::QName(std::string(), "initiator")));
 }
 
 // Verify that we can connect two endpoints with multi-step authentication.
diff --git a/remoting/protocol/libjingle_transport_factory.cc b/remoting/protocol/libjingle_transport_factory.cc
index e27b619..7a09d09 100644
--- a/remoting/protocol/libjingle_transport_factory.cc
+++ b/remoting/protocol/libjingle_transport_factory.cc
@@ -139,7 +139,7 @@ void LibjingleStreamTransport::Connect(
   // Create P2PTransportChannel, attach signal handlers and connect it.
   // TODO(sergeyu): Specify correct component ID for the channel.
   channel_.reset(new cricket::P2PTransportChannel(
-      "", 0, NULL, port_allocator_));
+      std::string(), 0, NULL, port_allocator_));
   channel_->SetIceCredentials(ice_username_fragment_, ice_password_);
   channel_->SignalRequestSignaling.connect(
       this, &LibjingleStreamTransport::OnRequestSignaling);
diff --git a/remoting/protocol/third_party_authenticator_unittest.cc b/remoting/protocol/third_party_authenticator_unittest.cc
index b787a62..0298877 100644
--- a/remoting/protocol/third_party_authenticator_unittest.cc
+++ b/remoting/protocol/third_party_authenticator_unittest.cc
@@ -153,7 +153,8 @@ TEST_F(ThirdPartyAuthenticatorTest, ClientNoSecret) {
   ASSERT_NO_FATAL_FAILURE(InitAuthenticators());
   ASSERT_NO_FATAL_FAILURE(RunHostInitiatedAuthExchange());
   ASSERT_EQ(Authenticator::PROCESSING_MESSAGE, client_->state());
-  ASSERT_NO_FATAL_FAILURE(token_fetcher_->OnTokenFetched(kToken, ""));
+  ASSERT_NO_FATAL_FAILURE(
+      token_fetcher_->OnTokenFetched(kToken, std::string()));
 
   // The end result is that the client rejected the connection, since it
   // couldn't fetch the secret.
@@ -167,7 +168,7 @@ TEST_F(ThirdPartyAuthenticatorTest, InvalidToken) {
   ASSERT_NO_FATAL_FAILURE(token_fetcher_->OnTokenFetched(
       kToken, kSharedSecret));
   ASSERT_EQ(Authenticator::PROCESSING_MESSAGE, host_->state());
-  ASSERT_NO_FATAL_FAILURE(token_validator_->OnTokenValidated(""));
+  ASSERT_NO_FATAL_FAILURE(token_validator_->OnTokenValidated(std::string()));
 
   // The end result is that the host rejected the token.
   ASSERT_EQ(Authenticator::REJECTED, host_->state());
@@ -177,7 +178,8 @@ TEST_F(ThirdPartyAuthenticatorTest, CannotFetchToken) {
   ASSERT_NO_FATAL_FAILURE(InitAuthenticators());
   ASSERT_NO_FATAL_FAILURE(RunHostInitiatedAuthExchange());
   ASSERT_EQ(Authenticator::PROCESSING_MESSAGE, client_->state());
-  ASSERT_NO_FATAL_FAILURE(token_fetcher_->OnTokenFetched("", ""));
+  ASSERT_NO_FATAL_FAILURE(
+      token_fetcher_->OnTokenFetched(std::string(), std::string()));
 
   // The end result is that the client rejected the connection, since it
   // couldn't fetch the token.
diff --git a/remoting/protocol/transport.cc b/remoting/protocol/transport.cc
index 4ccbcde..13ed29f 100644
--- a/remoting/protocol/transport.cc
+++ b/remoting/protocol/transport.cc
@@ -20,7 +20,7 @@ std::string TransportRoute::GetTypeString(RouteType type) {
       return "relay";
   }
   NOTREACHED();
-  return "";
+  return std::string();
 }
 
 TransportRoute::TransportRoute() : type(DIRECT) {