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

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

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@193020 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 14 insertions, 13 deletions

diff --git a/remoting/jingle_glue/iq_sender_unittest.cc b/remoting/jingle_glue/iq_sender_unittest.cc
index b09f114..2876735 100644
--- a/remoting/jingle_glue/iq_sender_unittest.cc
+++ b/remoting/jingle_glue/iq_sender_unittest.cc
@@ -91,9 +91,9 @@ TEST_F(IqSenderTest, SendIq) {
   });
 
   scoped_ptr<XmlElement> response(new XmlElement(buzz::QN_IQ));
-  response->AddAttr(QName("", "type"), "result");
-  response->AddAttr(QName("", "id"), kStanzaId);
-  response->AddAttr(QName("", "from"), kTo);
+  response->AddAttr(QName(std::string(), "type"), "result");
+  response->AddAttr(QName(std::string(), "id"), kStanzaId);
+  response->AddAttr(QName(std::string(), "from"), kTo);
 
   XmlElement* result = new XmlElement(
       QName("test:namespace", "response-body"));
@@ -123,9 +123,9 @@ TEST_F(IqSenderTest, InvalidFrom) {
   });
 
   scoped_ptr<XmlElement> response(new XmlElement(buzz::QN_IQ));
-  response->AddAttr(QName("", "type"), "result");
-  response->AddAttr(QName("", "id"), kStanzaId);
-  response->AddAttr(QName("", "from"), "different_user@domain.com");
+  response->AddAttr(QName(std::string(), "type"), "result");
+  response->AddAttr(QName(std::string(), "id"), kStanzaId);
+  response->AddAttr(QName(std::string(), "from"), "different_user@domain.com");
 
   XmlElement* result = new XmlElement(
       QName("test:namespace", "response-body"));
@@ -143,9 +143,9 @@ TEST_F(IqSenderTest, IdMatchingHack) {
   });
 
   scoped_ptr<XmlElement> response(new XmlElement(buzz::QN_IQ));
-  response->AddAttr(QName("", "type"), "result");
-  response->AddAttr(QName("", "id"), "DIFFERENT_ID");
-  response->AddAttr(QName("", "from"), kTo);
+  response->AddAttr(QName(std::string(), "type"), "result");
+  response->AddAttr(QName(std::string(), "id"), "DIFFERENT_ID");
+  response->AddAttr(QName(std::string(), "from"), kTo);
 
   XmlElement* result = new XmlElement(
       QName("test:namespace", "response-body"));
diff --git a/remoting/jingle_glue/xmpp_signal_strategy.cc b/remoting/jingle_glue/xmpp_signal_strategy.cc
index 51bbade..88fc9f3 100644
--- a/remoting/jingle_glue/xmpp_signal_strategy.cc
+++ b/remoting/jingle_glue/xmpp_signal_strategy.cc
@@ -91,9 +91,10 @@ void XmppSignalStrategy::Connect() {
 
   task_runner_.reset(new jingle_glue::TaskPump());
   xmpp_client_ = new buzz::XmppClient(task_runner_.get());
-  xmpp_client_->Connect(settings, "", socket, CreatePreXmppAuth(settings));
-  xmpp_client_->SignalStateChange.connect(
-      this, &XmppSignalStrategy::OnConnectionStateChanged);
+  xmpp_client_->Connect(
+      settings, std::string(), socket, CreatePreXmppAuth(settings));
+  xmpp_client_->SignalStateChange
+      .connect(this, &XmppSignalStrategy::OnConnectionStateChanged);
   xmpp_client_->engine()->AddStanzaHandler(this, buzz::XmppEngine::HL_TYPE);
   xmpp_client_->Start();
 
@@ -156,7 +157,7 @@ std::string XmppSignalStrategy::GetNextId() {
   if (!xmpp_client_) {
     // If the connection has been terminated then it doesn't matter
     // what Id we return.
-    return "";
+    return std::string();
   }
   return xmpp_client_->NextId();
 }