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

9 files changed, 54 insertions, 30 deletions

diff --git a/net/tools/dump_cache/url_to_filename_encoder_unittest.cc b/net/tools/dump_cache/url_to_filename_encoder_unittest.cc
index 2e09e0b..23bbc6d 100644
--- a/net/tools/dump_cache/url_to_filename_encoder_unittest.cc
+++ b/net/tools/dump_cache/url_to_filename_encoder_unittest.cc
@@ -57,7 +57,8 @@ class UrlToFilenameEncoderTest : public ::testing::Test {
 
   void Validate(const string& in_word, const string& gold_word) {
     string escaped_word, url;
-    UrlToFilenameEncoder::EncodeSegment("", in_word, '/', &escaped_word);
+    UrlToFilenameEncoder::EncodeSegment(
+        std::string(), in_word, '/', &escaped_word);
     EXPECT_EQ(gold_word, escaped_word);
     CheckSegmentLength(escaped_word);
     CheckValidChars(escaped_word, '\\');
@@ -67,7 +68,8 @@ class UrlToFilenameEncoderTest : public ::testing::Test {
 
   void ValidateAllSegmentsSmall(const string& in_word) {
     string escaped_word, url;
-    UrlToFilenameEncoder::EncodeSegment("", in_word, '/', &escaped_word);
+    UrlToFilenameEncoder::EncodeSegment(
+        std::string(), in_word, '/', &escaped_word);
     CheckSegmentLength(escaped_word);
     CheckValidChars(escaped_word, '\\');
     UrlToFilenameEncoder::Decode(escaped_word, '/', &url);
@@ -106,13 +108,13 @@ class UrlToFilenameEncoderTest : public ::testing::Test {
 
   void ValidateUrlOldNew(const string& url, const string& gold_old_filename,
                          const string& gold_new_filename) {
-    ValidateUrl(url, "", true, gold_old_filename);
-    ValidateUrl(url, "", false, gold_new_filename);
+    ValidateUrl(url, std::string(), true, gold_old_filename);
+    ValidateUrl(url, std::string(), false, gold_new_filename);
   }
 
   void ValidateEncodeSame(const string& url1, const string& url2) {
-    string filename1 = UrlToFilenameEncoder::Encode(url1, "", false);
-    string filename2 = UrlToFilenameEncoder::Encode(url2, "", false);
+    string filename1 = UrlToFilenameEncoder::Encode(url1, std::string(), false);
+    string filename2 = UrlToFilenameEncoder::Encode(url2, std::string(), false);
     EXPECT_EQ(filename1, filename2);
   }
 
@@ -121,7 +123,7 @@ class UrlToFilenameEncoderTest : public ::testing::Test {
 };
 
 TEST_F(UrlToFilenameEncoderTest, DoesNotEscape) {
-  ValidateNoChange("");
+  ValidateNoChange(std::string());
   ValidateNoChange("abcdefg");
   ValidateNoChange("abcdefghijklmnopqrstuvwxyz");
   ValidateNoChange("ZYXWVUT");
@@ -193,7 +195,8 @@ TEST_F(UrlToFilenameEncoderTest, EncodeUrlCorrectly) {
 
   // From bug: Double slash preserved.
   ValidateUrl("http://www.foo.com/u?site=http://www.google.com/index.html",
-              "", false,
+              std::string(),
+              false,
               "www.foo.com" + dir_sep_ + "u" + escape_ + "3Fsite=http" +
               escape_ + "3A" + dir_sep_ + escape_ + "2Fwww.google.com" +
               dir_sep_ + "index.html" + escape_);
@@ -326,7 +329,8 @@ TEST_F(UrlToFilenameEncoderTest, BackslashSeparator) {
   string long_word;
   string escaped_word;
   long_word.append(UrlToFilenameEncoder::kMaximumSubdirectoryLength + 1, 'x');
-  UrlToFilenameEncoder::EncodeSegment("", long_word, '\\', &escaped_word);
+  UrlToFilenameEncoder::EncodeSegment(
+      std::string(), long_word, '\\', &escaped_word);
 
   // check that one backslash, plus the escape ",-", and the ending , got added.
   EXPECT_EQ(long_word.size() + 4, escaped_word.size());
diff --git a/net/tools/fetch/fetch_server.cc b/net/tools/fetch/fetch_server.cc
index 830cd18..34c7c83 100644
--- a/net/tools/fetch/fetch_server.cc
+++ b/net/tools/fetch/fetch_server.cc
@@ -36,7 +36,8 @@ int main(int argc, char**argv) {
 
   // Do work here.
   MessageLoop loop;
-  HttpServer server("", 80);   // TODO(mbelshe): make port configurable
+  HttpServer server(std::string(),
+                    80);  // TODO(mbelshe): make port configurable
   MessageLoop::current()->Run();
 
   if (parsed_command_line.HasSwitch("stats")) {
diff --git a/net/tools/flip_server/acceptor_thread.cc b/net/tools/flip_server/acceptor_thread.cc
index b16d181..ed8a3ec 100644
--- a/net/tools/flip_server/acceptor_thread.cc
+++ b/net/tools/flip_server/acceptor_thread.cc
@@ -105,7 +105,9 @@ void SMAcceptorThread::HandleConnection(int server_fd,
                                       NULL,
                                       &epoll_server_,
                                       server_fd,
-                                      "", "", remote_ip,
+                                      std::string(),
+                                      std::string(),
+                                      remote_ip,
                                       use_ssl_);
   if (server_connection->initialized())
     active_server_connections_.push_back(server_connection);
diff --git a/net/tools/flip_server/flip_in_mem_edsm_server.cc b/net/tools/flip_server/flip_in_mem_edsm_server.cc
index 8ba1505..15fb9644 100644
--- a/net/tools/flip_server/flip_in_mem_edsm_server.cc
+++ b/net/tools/flip_server/flip_in_mem_edsm_server.cc
@@ -335,11 +335,16 @@ int main (int argc, char**argv)
     std::string value = cl.GetSwitchValueASCII("spdy-server");
     std::vector<std::string> valueArgs = split(value, ',');
     while (valueArgs.size() < 4)
-      valueArgs.push_back("");
+      valueArgs.push_back(std::string());
     g_proxy_config.AddAcceptor(net::FLIP_HANDLER_SPDY_SERVER,
-                               valueArgs[0], valueArgs[1],
-                               valueArgs[2], valueArgs[3],
-                               "", "", "", "",
+                               valueArgs[0],
+                               valueArgs[1],
+                               valueArgs[2],
+                               valueArgs[3],
+                               std::string(),
+                               std::string(),
+                               std::string(),
+                               std::string(),
                                0,
                                FLAGS_accept_backlog_size,
                                FLAGS_disable_nagle,
@@ -356,11 +361,16 @@ int main (int argc, char**argv)
     std::string value = cl.GetSwitchValueASCII("http-server");
     std::vector<std::string> valueArgs = split(value, ',');
     while (valueArgs.size() < 4)
-      valueArgs.push_back("");
+      valueArgs.push_back(std::string());
     g_proxy_config.AddAcceptor(net::FLIP_HANDLER_HTTP_SERVER,
-                               valueArgs[0], valueArgs[1],
-                               valueArgs[2], valueArgs[3],
-                               "", "", "", "",
+                               valueArgs[0],
+                               valueArgs[1],
+                               valueArgs[2],
+                               valueArgs[3],
+                               std::string(),
+                               std::string(),
+                               std::string(),
+                               std::string(),
                                0,
                                FLAGS_accept_backlog_size,
                                FLAGS_disable_nagle,
diff --git a/net/tools/flip_server/spdy_interface.cc b/net/tools/flip_server/spdy_interface.cc
index 1c34e79..649e99e 100644
--- a/net/tools/flip_server/spdy_interface.cc
+++ b/net/tools/flip_server/spdy_interface.cc
@@ -112,9 +112,14 @@ SMInterface* SpdySM::FindOrMakeNewSMConnectionInterface(
   }
 
   sm_http_interface->InitSMInterface(this, server_idx);
-  sm_http_interface->InitSMConnection(NULL, sm_http_interface,
-                                      epoll_server_, -1,
-                                      server_ip, server_port, "", false);
+  sm_http_interface->InitSMConnection(NULL,
+                                      sm_http_interface,
+                                      epoll_server_,
+                                      -1,
+                                      server_ip,
+                                      server_port,
+                                      std::string(),
+                                      false);
 
   return sm_http_interface;
 }
diff --git a/net/tools/flip_server/streamer_interface.cc b/net/tools/flip_server/streamer_interface.cc
index 9e6e6c8..b1612e7 100644
--- a/net/tools/flip_server/streamer_interface.cc
+++ b/net/tools/flip_server/streamer_interface.cc
@@ -131,11 +131,13 @@ int StreamerSM::PostAcceptHook() {
   }
   // The Streamer interface is used to stream HTTPS connections, so we
   // will always use the https_server_ip/port here.
-  sm_other_interface_->InitSMConnection(NULL, sm_other_interface_,
-                                        epoll_server_, -1,
+  sm_other_interface_->InitSMConnection(NULL,
+                                        sm_other_interface_,
+                                        epoll_server_,
+                                        -1,
                                         acceptor_->https_server_ip_,
                                         acceptor_->https_server_port_,
-                                        "",
+                                        std::string(),
                                         false);
 
   return 1;
diff --git a/net/tools/quic/end_to_end_test.cc b/net/tools/quic/end_to_end_test.cc
index e98c4ea..cb14db8 100644
--- a/net/tools/quic/end_to_end_test.cc
+++ b/net/tools/quic/end_to_end_test.cc
@@ -234,7 +234,7 @@ TEST_F(EndToEndTest, SeparateFinPacket) {
 
   client_->SendMessage(request);
 
-  client_->SendData("", true);
+  client_->SendData(std::string(), true);
 
   client_->WaitForResponse();
   EXPECT_EQ(kFooResponseBody, client_->response_body());
@@ -243,7 +243,7 @@ TEST_F(EndToEndTest, SeparateFinPacket) {
   request.AddBody("foo", true);
 
   client_->SendMessage(request);
-  client_->SendData("", true);
+  client_->SendData(std::string(), true);
   client_->WaitForResponse();
   EXPECT_EQ(kFooResponseBody, client_->response_body());
   EXPECT_EQ(200ul, client_->response_headers()->parsed_response_code());
diff --git a/net/tools/quic/quic_client.cc b/net/tools/quic/quic_client.cc
index 4a61ab4..8acb85a 100644
--- a/net/tools/quic/quic_client.cc
+++ b/net/tools/quic/quic_client.cc
@@ -43,8 +43,8 @@ QuicClient::QuicClient(IPEndPoint server_address,
 
 QuicClient::~QuicClient() {
   if (connected()) {
-    session()->connection()->SendConnectionClosePacket(
-        QUIC_PEER_GOING_AWAY, "");
+    session()->connection()
+        ->SendConnectionClosePacket(QUIC_PEER_GOING_AWAY, std::string());
   }
 }
 
diff --git a/net/tools/quic/test_tools/quic_test_client.cc b/net/tools/quic/test_tools/quic_test_client.cc
index 53bc057..843af2f 100644
--- a/net/tools/quic/test_tools/quic_test_client.cc
+++ b/net/tools/quic/test_tools/quic_test_client.cc
@@ -85,7 +85,7 @@ string QuicTestClient::SendCustomSynchronousRequest(
 string QuicTestClient::SendSynchronousRequest(const string& uri) {
   if (SendRequest(uri) == 0) {
     DLOG(ERROR) << "Failed to the request for uri:" << uri;
-    return "";
+    return std::string();
   }
   WaitForResponse();
   return response_;