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

15 files changed, 103 insertions, 85 deletions

diff --git a/ppapi/cpp/dev/text_input_dev.cc b/ppapi/cpp/dev/text_input_dev.cc
index 3b38df8..657a0b3 100644
--- a/ppapi/cpp/dev/text_input_dev.cc
+++ b/ppapi/cpp/dev/text_input_dev.cc
@@ -54,7 +54,7 @@ TextInput_Dev::~TextInput_Dev() {
 
 void TextInput_Dev::RequestSurroundingText(uint32_t) {
   // Default implementation. Send a null range.
-  UpdateSurroundingText("", 0, 0);
+  UpdateSurroundingText(std::string(), 0, 0);
 }
 
 void TextInput_Dev::SetTextInputType(PP_TextInput_Type type) {
diff --git a/ppapi/examples/ime/ime.cc b/ppapi/examples/ime/ime.cc
index f5e2e44..6f3e655 100644
--- a/ppapi/examples/ime/ime.cc
+++ b/ppapi/examples/ime/ime.cc
@@ -245,7 +245,7 @@ class MyTextField {
       int32_t target_segment,
       const std::pair<uint32_t, uint32_t>& selection) {
     if (HasSelection() && !text.empty())
-      InsertText("");
+      InsertText(std::string());
     composition_ = text;
     segments_ = segments;
     target_segment_ = target_segment;
@@ -344,7 +344,7 @@ class MyTextField {
     if (!Focused())
       return;
     if (HasSelection()) {
-      InsertText("");
+      InsertText(std::string());
     } else {
       size_t i = GetNextCharOffsetUtf8(utf8_text_, caret_pos_);
       utf8_text_.erase(caret_pos_, i - caret_pos_);
@@ -356,7 +356,7 @@ class MyTextField {
     if (!Focused())
       return;
     if (HasSelection()) {
-      InsertText("");
+      InsertText(std::string());
     } else if (caret_pos_ != 0) {
       size_t i = GetPrevCharOffsetUtf8(utf8_text_, caret_pos_);
       utf8_text_.erase(i, caret_pos_ - i);
@@ -565,8 +565,10 @@ class MyInstance : public pp::Instance {
          it != textfield_.end();
          ++it) {
       if (it->Focused()) {
-        it->SetComposition("", std::vector< std::pair<uint32_t, uint32_t> >(),
-                           0, std::make_pair(0, 0));
+        it->SetComposition(std::string(),
+                           std::vector<std::pair<uint32_t, uint32_t> >(),
+                           0,
+                           std::make_pair(0, 0));
         return true;
       }
     }
diff --git a/ppapi/native_client/src/trusted/plugin/plugin.cc b/ppapi/native_client/src/trusted/plugin/plugin.cc
index e1f3ad9..7b2f0a9 100644
--- a/ppapi/native_client/src/trusted/plugin/plugin.cc
+++ b/ppapi/native_client/src/trusted/plugin/plugin.cc
@@ -677,7 +677,6 @@ bool Plugin::Init(uint32_t argc, const char* argn[], const char* argv[]) {
   return status;
 }
 
-
 Plugin::Plugin(PP_Instance pp_instance)
     : pp::InstancePrivate(pp_instance),
       scriptable_plugin_(NULL),
@@ -688,7 +687,6 @@ Plugin::Plugin(PP_Instance pp_instance)
       nacl_ready_state_(UNSENT),
       nexe_error_reported_(false),
       wrapper_factory_(NULL),
-      last_error_string_(""),
       enable_dev_interfaces_(false),
       is_installed_(false),
       init_time_(0),
diff --git a/ppapi/native_client/src/trusted/plugin/plugin_error.h b/ppapi/native_client/src/trusted/plugin/plugin_error.h
index 90c0284..f02ef83 100644
--- a/ppapi/native_client/src/trusted/plugin/plugin_error.h
+++ b/ppapi/native_client/src/trusted/plugin/plugin_error.h
@@ -109,7 +109,7 @@ class ErrorInfo {
   }
 
   void Reset() {
-    SetReport(ERROR_UNKNOWN, "");
+    SetReport(ERROR_UNKNOWN, std::string());
   }
 
   void SetReport(PluginErrorCode error_code, const std::string& message) {
diff --git a/ppapi/native_client/src/trusted/plugin/pnacl_translate_thread.cc b/ppapi/native_client/src/trusted/plugin/pnacl_translate_thread.cc
index a7d3f24..ff0982e 100644
--- a/ppapi/native_client/src/trusted/plugin/pnacl_translate_thread.cc
+++ b/ppapi/native_client/src/trusted/plugin/pnacl_translate_thread.cc
@@ -224,9 +224,7 @@ void PnaclTranslateThread::DoTranslate() {
   }
   PLUGIN_PRINTF(("PnaclTranslateThread done with chunks\n"));
   // Finish llc.
-  if(!llc_subprocess_->InvokeSrpcMethod("StreamEnd",
-                                       "",
-                                       &params)) {
+  if (!llc_subprocess_->InvokeSrpcMethod("StreamEnd", std::string(), &params)) {
     PLUGIN_PRINTF(("PnaclTranslateThread StreamEnd failed\n"));
     if (llc_subprocess_->srpc_client()->GetLastError() ==
         NACL_SRPC_RESULT_APP_ERROR) {
diff --git a/ppapi/native_client/src/trusted/plugin/service_runtime.cc b/ppapi/native_client/src/trusted/plugin/service_runtime.cc
index 00f64c7..68a50d3 100644
--- a/ppapi/native_client/src/trusted/plugin/service_runtime.cc
+++ b/ppapi/native_client/src/trusted/plugin/service_runtime.cc
@@ -846,7 +846,7 @@ nacl::string ServiceRuntime::GetCrashLogOutput() {
   if (NULL != subprocess_.get()) {
     return subprocess_->GetCrashLogOutput();
   } else {
-    return "";
+    return std::string();
   }
 }
 
diff --git a/ppapi/proxy/audio_input_resource.cc b/ppapi/proxy/audio_input_resource.cc
index 5f700ec..4f321c2 100644
--- a/ppapi/proxy/audio_input_resource.cc
+++ b/ppapi/proxy/audio_input_resource.cc
@@ -217,7 +217,10 @@ void AudioInputResource::SetStreamInfo(
   shared_memory_size_ = shared_memory_size;
 
   if (!shared_memory_->Map(shared_memory_size_)) {
-    PpapiGlobals::Get()->LogWithSource(pp_instance(), PP_LOGLEVEL_WARNING, "",
+    PpapiGlobals::Get()->LogWithSource(
+        pp_instance(),
+        PP_LOGLEVEL_WARNING,
+        std::string(),
         "Failed to map shared memory for PPB_AudioInput_Shared.");
   }
 
diff --git a/ppapi/shared_impl/ppb_audio_shared.cc b/ppapi/shared_impl/ppb_audio_shared.cc
index f275559..f6d0cac 100644
--- a/ppapi/shared_impl/ppb_audio_shared.cc
+++ b/ppapi/shared_impl/ppb_audio_shared.cc
@@ -80,8 +80,11 @@ void PPB_Audio_Shared::SetStreamInfo(
 
   if (!shared_memory_->Map(
           media::TotalSharedMemorySizeInBytes(shared_memory_size_))) {
-    PpapiGlobals::Get()->LogWithSource(instance, PP_LOGLEVEL_WARNING, "",
-      "Failed to map shared memory for PPB_Audio_Shared.");
+    PpapiGlobals::Get()->LogWithSource(
+        instance,
+        PP_LOGLEVEL_WARNING,
+        std::string(),
+        "Failed to map shared memory for PPB_Audio_Shared.");
   } else {
     audio_bus_ = media::AudioBus::WrapMemory(
         kChannels, sample_frame_count, shared_memory_->memory());
diff --git a/ppapi/tests/test_file_ref.cc b/ppapi/tests/test_file_ref.cc
index 2dfea85..f3217f9 100644
--- a/ppapi/tests/test_file_ref.cc
+++ b/ppapi/tests/test_file_ref.cc
@@ -85,7 +85,7 @@ void TestFileRef::RunTests(const std::string& filter) {
 std::string TestFileRef::TestCreate() {
   std::vector<std::string> invalid_paths;
   invalid_paths.push_back("invalid_path");  // no '/' at the first character
-  invalid_paths.push_back("");  // empty path
+  invalid_paths.push_back(std::string());   // empty path
   // The following are directory traversal checks
   invalid_paths.push_back("..");
   invalid_paths.push_back("/../invalid_path");
diff --git a/ppapi/tests/test_flash_clipboard.cc b/ppapi/tests/test_flash_clipboard.cc
index e38c145..8eb756b 100644
--- a/ppapi/tests/test_flash_clipboard.cc
+++ b/ppapi/tests/test_flash_clipboard.cc
@@ -253,7 +253,7 @@ std::string TestFlashClipboard::TestInvalidFormat() {
 std::string TestFlashClipboard::TestRegisterCustomFormat() {
   // Test an empty name is rejected.
   uint32_t format_id =
-      pp::flash::Clipboard::RegisterCustomFormat(instance_, "");
+      pp::flash::Clipboard::RegisterCustomFormat(instance_, std::string());
   ASSERT_EQ(format_id, PP_FLASH_CLIPBOARD_FORMAT_INVALID);
 
   // Test a valid format name.
diff --git a/ppapi/tests/test_flash_file.cc b/ppapi/tests/test_flash_file.cc
index 86100d9..e5a8ee9 100644
--- a/ppapi/tests/test_flash_file.cc
+++ b/ppapi/tests/test_flash_file.cc
@@ -285,12 +285,10 @@ std::string TestFlashFile::TestGetDirContents() {
   CloseFileHandle(file_handle);
   ASSERT_TRUE(FileModuleLocal::CreateDir(instance_, dirname));
 
-  ASSERT_TRUE(FileModuleLocal::GetDirContents(instance_, "", &result));
-  FileModuleLocal::DirEntry expected[] =
-    { {"..", true},
-      {filename, false},
-      {dirname, true}
-    };
+  ASSERT_TRUE(
+      FileModuleLocal::GetDirContents(instance_, std::string(), &result));
+  FileModuleLocal::DirEntry expected[] = { { "..", true }, { filename, false },
+                                           { dirname, true } };
   size_t expected_size = sizeof(expected) / sizeof(expected[0]);
 
   std::sort(expected, expected + expected_size, DirEntryLessThan);
@@ -329,7 +327,8 @@ std::string TestFlashFile::TestCreateTemporaryFile() {
 std::string TestFlashFile::GetItemCountUnderModuleLocalRoot(
     size_t* item_count) {
   std::vector<FileModuleLocal::DirEntry> contents;
-  ASSERT_TRUE(FileModuleLocal::GetDirContents(instance_, "", &contents));
+  ASSERT_TRUE(
+      FileModuleLocal::GetDirContents(instance_, std::string(), &contents));
   *item_count = contents.size();
   PASS();
 }
diff --git a/ppapi/tests/test_ime_input_event.cc b/ppapi/tests/test_ime_input_event.cc
index 804e17d7a..500fcbb 100644
--- a/ppapi/tests/test_ime_input_event.cc
+++ b/ppapi/tests/test_ime_input_event.cc
@@ -357,11 +357,11 @@ std::string TestImeInputEvent::TestImeCancel() {
   expected_events_.clear();
   expected_events_.push_back(CreateImeCompositionStartEvent());
   expected_events_.push_back(update_event);
-  expected_events_.push_back(CreateImeCompositionEndEvent(""));
+  expected_events_.push_back(CreateImeCompositionEndEvent(std::string()));
 
   // Simulate the case when IME canceled composition.
   ASSERT_TRUE(SimulateInputEvent(update_event));
-  ASSERT_TRUE(SimulateInputEvent(CreateImeCompositionEndEvent("")));
+  ASSERT_TRUE(SimulateInputEvent(CreateImeCompositionEndEvent(std::string())));
 
   ASSERT_TRUE(expected_events_.empty());
   PASS();
@@ -417,7 +417,7 @@ std::string TestImeInputEvent::TestImeUnawareCancel() {
 
   // Test for IME-unaware plugins. Cancel won't issue any events.
   ASSERT_TRUE(SimulateInputEvent(update_event));
-  ASSERT_TRUE(SimulateInputEvent(CreateImeCompositionEndEvent("")));
+  ASSERT_TRUE(SimulateInputEvent(CreateImeCompositionEndEvent(std::string())));
 
   ASSERT_TRUE(expected_events_.empty());
   PASS();
diff --git a/ppapi/tests/test_url_loader.cc b/ppapi/tests/test_url_loader.cc
index 112a483..320167a 100644
--- a/ppapi/tests/test_url_loader.cc
+++ b/ppapi/tests/test_url_loader.cc
@@ -375,7 +375,7 @@ std::string TestURLLoader::TestEmptyDataPOST() {
   request.SetURL("/echo");
   request.SetMethod("POST");
   request.AppendDataToBody("", 0);
-  return LoadAndCompareBody(request, "");
+  return LoadAndCompareBody(request, std::string());
 }
 
 std::string TestURLLoader::TestBinaryDataPOST() {
@@ -558,11 +558,12 @@ std::string TestURLLoader::TestUntrustedHttpRequests() {
   // valid token (containing special characters like CR, LF).
   // http://www.w3.org/TR/XMLHttpRequest/
   {
-    ASSERT_EQ(OpenUntrusted("cOnNeCt", ""), PP_ERROR_NOACCESS);
-    ASSERT_EQ(OpenUntrusted("tRaCk", ""), PP_ERROR_NOACCESS);
-    ASSERT_EQ(OpenUntrusted("tRaCe", ""), PP_ERROR_NOACCESS);
-    ASSERT_EQ(OpenUntrusted("POST\x0d\x0ax-csrf-token:\x20test1234", ""),
-                            PP_ERROR_NOACCESS);
+    ASSERT_EQ(OpenUntrusted("cOnNeCt", std::string()), PP_ERROR_NOACCESS);
+    ASSERT_EQ(OpenUntrusted("tRaCk", std::string()), PP_ERROR_NOACCESS);
+    ASSERT_EQ(OpenUntrusted("tRaCe", std::string()), PP_ERROR_NOACCESS);
+    ASSERT_EQ(
+        OpenUntrusted("POST\x0d\x0ax-csrf-token:\x20test1234", std::string()),
+        PP_ERROR_NOACCESS);
   }
   // HTTP methods are restricted only for untrusted loaders. Try all headers
   // that are forbidden by http://www.w3.org/TR/XMLHttpRequest/.
@@ -619,9 +620,9 @@ std::string TestURLLoader::TestUntrustedHttpRequests() {
 std::string TestURLLoader::TestTrustedHttpRequests() {
   // Trusted requests can use restricted methods.
   {
-    ASSERT_EQ(OpenTrusted("cOnNeCt", ""), PP_OK);
-    ASSERT_EQ(OpenTrusted("tRaCk", ""), PP_OK);
-    ASSERT_EQ(OpenTrusted("tRaCe", ""), PP_OK);
+    ASSERT_EQ(OpenTrusted("cOnNeCt", std::string()), PP_OK);
+    ASSERT_EQ(OpenTrusted("tRaCk", std::string()), PP_OK);
+    ASSERT_EQ(OpenTrusted("tRaCe", std::string()), PP_OK);
   }
   // Trusted requests can use restricted headers.
   {
diff --git a/ppapi/tests/test_websocket.cc b/ppapi/tests/test_websocket.cc
index e61185d..61a8e19 100644
--- a/ppapi/tests/test_websocket.cc
+++ b/ppapi/tests/test_websocket.cc
@@ -350,18 +350,18 @@ std::string TestWebSocket::TestUninitializedPropertiesAccess() {
   ASSERT_EQ(0U, close_code);
 
   PP_Var close_reason = websocket_interface_->GetCloseReason(ws);
-  ASSERT_TRUE(AreEqualWithString(close_reason, ""));
+  ASSERT_TRUE(AreEqualWithString(close_reason, std::string()));
   ReleaseVar(close_reason);
 
   PP_Bool close_was_clean = websocket_interface_->GetCloseWasClean(ws);
   ASSERT_EQ(PP_FALSE, close_was_clean);
 
   PP_Var extensions = websocket_interface_->GetExtensions(ws);
-  ASSERT_TRUE(AreEqualWithString(extensions, ""));
+  ASSERT_TRUE(AreEqualWithString(extensions, std::string()));
   ReleaseVar(extensions);
 
   PP_Var protocol = websocket_interface_->GetProtocol(ws);
-  ASSERT_TRUE(AreEqualWithString(protocol, ""));
+  ASSERT_TRUE(AreEqualWithString(protocol, std::string()));
   ReleaseVar(protocol);
 
   PP_WebSocketReadyState ready_state =
@@ -369,7 +369,7 @@ std::string TestWebSocket::TestUninitializedPropertiesAccess() {
   ASSERT_EQ(PP_WEBSOCKETREADYSTATE_INVALID, ready_state);
 
   PP_Var url = websocket_interface_->GetURL(ws);
-  ASSERT_TRUE(AreEqualWithString(url, ""));
+  ASSERT_TRUE(AreEqualWithString(url, std::string()));
   ReleaseVar(url);
 
   core_interface_->ReleaseResource(ws);
@@ -398,7 +398,7 @@ std::string TestWebSocket::TestInvalidConnect() {
 
   for (int i = 0; kInvalidURLs[i]; ++i) {
     int32_t result;
-    ws = Connect(kInvalidURLs[i], &result, "");
+    ws = Connect(kInvalidURLs[i], &result, std::string());
     ASSERT_TRUE(ws);
     ASSERT_EQ(PP_ERROR_BADARGUMENT, result);
 
@@ -448,7 +448,7 @@ std::string TestWebSocket::TestProtocols() {
 std::string TestWebSocket::TestGetURL() {
   for (int i = 0; kInvalidURLs[i]; ++i) {
     int32_t result;
-    PP_Resource ws = Connect(kInvalidURLs[i], &result, "");
+    PP_Resource ws = Connect(kInvalidURLs[i], &result, std::string());
     ASSERT_TRUE(ws);
     PP_Var url = websocket_interface_->GetURL(ws);
     ASSERT_TRUE(AreEqualWithString(url, kInvalidURLs[i]));
@@ -463,11 +463,11 @@ std::string TestWebSocket::TestGetURL() {
 
 std::string TestWebSocket::TestValidConnect() {
   int32_t result;
-  PP_Resource ws = Connect(GetFullURL(kEchoServerURL), &result, "");
+  PP_Resource ws = Connect(GetFullURL(kEchoServerURL), &result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, result);
   PP_Var extensions = websocket_interface_->GetExtensions(ws);
-  ASSERT_TRUE(AreEqualWithString(extensions, ""));
+  ASSERT_TRUE(AreEqualWithString(extensions, std::string()));
   core_interface_->ReleaseResource(ws);
   ReleaseVar(extensions);
 
@@ -489,7 +489,7 @@ std::string TestWebSocket::TestInvalidClose() {
 
   // Close with bad arguments.
   int32_t result;
-  ws = Connect(GetFullURL(kEchoServerURL), &result, "");
+  ws = Connect(GetFullURL(kEchoServerURL), &result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, result);
   callback.WaitForResult(websocket_interface_->Close(
@@ -498,7 +498,7 @@ std::string TestWebSocket::TestInvalidClose() {
   core_interface_->ReleaseResource(ws);
 
   // Close with PP_VARTYPE_NULL.
-  ws = Connect(GetFullURL(kEchoServerURL), &result, "");
+  ws = Connect(GetFullURL(kEchoServerURL), &result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, result);
   callback.WaitForResult(websocket_interface_->Close(
@@ -508,7 +508,7 @@ std::string TestWebSocket::TestInvalidClose() {
   core_interface_->ReleaseResource(ws);
 
   // Close with PP_VARTYPE_NULL and ongoing receive message.
-  ws = Connect(GetFullURL(kEchoServerURL), &result, "");
+  ws = Connect(GetFullURL(kEchoServerURL), &result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, result);
   PP_Var receive_message_var;
@@ -532,7 +532,7 @@ std::string TestWebSocket::TestInvalidClose() {
   core_interface_->ReleaseResource(ws);
 
   // Close twice.
-  ws = Connect(GetFullURL(kEchoServerURL), &result, "");
+  ws = Connect(GetFullURL(kEchoServerURL), &result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, result);
   result = websocket_interface_->Close(
@@ -569,7 +569,7 @@ std::string TestWebSocket::TestValidClose() {
 
   // Close.
   int32_t result;
-  PP_Resource ws = Connect(GetFullURL(kEchoServerURL), &result, "");
+  PP_Resource ws = Connect(GetFullURL(kEchoServerURL), &result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, result);
   callback.WaitForResult(websocket_interface_->Close(
@@ -580,7 +580,7 @@ std::string TestWebSocket::TestValidClose() {
   core_interface_->ReleaseResource(ws);
 
   // Close without code and reason.
-  ws = Connect(GetFullURL(kEchoServerURL), &result, "");
+  ws = Connect(GetFullURL(kEchoServerURL), &result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, result);
   callback.WaitForResult(websocket_interface_->Close(
@@ -590,7 +590,7 @@ std::string TestWebSocket::TestValidClose() {
   core_interface_->ReleaseResource(ws);
 
   // Close with PP_VARTYPE_UNDEFINED.
-  ws = Connect(GetFullURL(kEchoServerURL), &result, "");
+  ws = Connect(GetFullURL(kEchoServerURL), &result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, result);
   callback.WaitForResult(websocket_interface_->Close(
@@ -620,7 +620,7 @@ std::string TestWebSocket::TestValidClose() {
   // Close in closing.
   // The first close will be done successfully, then the second one failed with
   // with PP_ERROR_INPROGRESS immediately.
-  ws = Connect(GetFullURL(kEchoServerURL), &result, "");
+  ws = Connect(GetFullURL(kEchoServerURL), &result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, result);
   result = websocket_interface_->Close(
@@ -636,7 +636,7 @@ std::string TestWebSocket::TestValidClose() {
   core_interface_->ReleaseResource(ws);
 
   // Close with ongoing receive message.
-  ws = Connect(GetFullURL(kEchoServerURL), &result, "");
+  ws = Connect(GetFullURL(kEchoServerURL), &result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, result);
   PP_Var receive_message_var;
@@ -655,7 +655,7 @@ std::string TestWebSocket::TestValidClose() {
   core_interface_->ReleaseResource(ws);
 
   // Close with PP_VARTYPE_UNDEFINED and ongoing receive message.
-  ws = Connect(GetFullURL(kEchoServerURL), &result, "");
+  ws = Connect(GetFullURL(kEchoServerURL), &result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, result);
   result = websocket_interface_->ReceiveMessage(
@@ -673,7 +673,8 @@ std::string TestWebSocket::TestValidClose() {
   core_interface_->ReleaseResource(ws);
 
   // Server initiated closing handshake.
-  ws = Connect(GetFullURL(kCloseWithCodeAndReasonServerURL), &result, "");
+  ws = Connect(
+      GetFullURL(kCloseWithCodeAndReasonServerURL), &result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, result);
   // Text messsage "1000 bye" requests the server to initiate closing handshake
@@ -720,7 +721,8 @@ std::string TestWebSocket::TestGetProtocol() {
 std::string TestWebSocket::TestTextSendReceive() {
   // Connect to test echo server.
   int32_t connect_result;
-  PP_Resource ws = Connect(GetFullURL(kEchoServerURL), &connect_result, "");
+  PP_Resource ws =
+      Connect(GetFullURL(kEchoServerURL), &connect_result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, connect_result);
 
@@ -747,7 +749,8 @@ std::string TestWebSocket::TestTextSendReceive() {
 std::string TestWebSocket::TestBinarySendReceive() {
   // Connect to test echo server.
   int32_t connect_result;
-  PP_Resource ws = Connect(GetFullURL(kEchoServerURL), &connect_result, "");
+  PP_Resource ws =
+      Connect(GetFullURL(kEchoServerURL), &connect_result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, connect_result);
 
@@ -776,7 +779,8 @@ std::string TestWebSocket::TestBinarySendReceive() {
 std::string TestWebSocket::TestStressedSendReceive() {
   // Connect to test echo server.
   int32_t connect_result;
-  PP_Resource ws = Connect(GetFullURL(kEchoServerURL), &connect_result, "");
+  PP_Resource ws =
+      Connect(GetFullURL(kEchoServerURL), &connect_result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, connect_result);
 
@@ -836,7 +840,8 @@ std::string TestWebSocket::TestStressedSendReceive() {
 std::string TestWebSocket::TestBufferedAmount() {
   // Connect to test echo server.
   int32_t connect_result;
-  PP_Resource ws = Connect(GetFullURL(kEchoServerURL), &connect_result, "");
+  PP_Resource ws =
+      Connect(GetFullURL(kEchoServerURL), &connect_result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, connect_result);
 
@@ -876,7 +881,7 @@ std::string TestWebSocket::TestBufferedAmount() {
 
   // After connection closure, all sending requests fail and just increase
   // the bufferedAmount property.
-  PP_Var empty_string = CreateVarString("");
+  PP_Var empty_string = CreateVarString(std::string());
   result = websocket_interface_->SendMessage(ws, empty_string);
   ASSERT_EQ(PP_ERROR_FAILED, result);
   buffered_amount = websocket_interface_->GetBufferedAmount(ws);
@@ -919,7 +924,7 @@ std::string TestWebSocket::TestAbortCallsWithCallback() {
   ASSERT_EQ(PP_ERROR_ABORTED, connect_callback.result());
 
   // Test the behavior for Close().
-  ws = Connect(url, &result, "");
+  ws = Connect(url, &result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, result);
   PP_Var reason_var = CreateVarString("abort");
@@ -936,7 +941,7 @@ std::string TestWebSocket::TestAbortCallsWithCallback() {
 
   // Test the behavior for ReceiveMessage().
   // Make sure the simplest case to wait for data which never arrives, here.
-  ws = Connect(url, &result, "");
+  ws = Connect(url, &result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, result);
   PP_Var receive_var;
@@ -952,7 +957,7 @@ std::string TestWebSocket::TestAbortCallsWithCallback() {
 
   // Release the resource in the aborting receive completion callback which is
   // introduced by calling Close().
-  ws = Connect(url, &result, "");
+  ws = Connect(url, &result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, result);
   result = websocket_interface_->ReceiveMessage(
@@ -986,7 +991,7 @@ std::string TestWebSocket::TestAbortSendMessageCall() {
 
   int32_t result;
   std::string url = GetFullURL(kEchoServerURL);
-  PP_Resource ws = Connect(url, &result, "");
+  PP_Resource ws = Connect(url, &result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, result);
   result = websocket_interface_->SendMessage(ws, large_var);
@@ -1001,7 +1006,7 @@ std::string TestWebSocket::TestAbortCloseCall() {
   // Release the resource in the close completion callback.
   int32_t result;
   std::string url = GetFullURL(kEchoServerURL);
-  PP_Resource ws = Connect(url, &result, "");
+  PP_Resource ws = Connect(url, &result, std::string());
   ASSERT_TRUE(ws);
   ASSERT_EQ(PP_OK, result);
   TestCompletionCallback close_callback(
@@ -1034,7 +1039,7 @@ std::string TestWebSocket::TestAbortReceiveMessageCall() {
   // released while the next message is going to be received.
   const int trial_count = 8;
   for (int trial = 1; trial <= trial_count; trial++) {
-    ws = Connect(url, &result, "");
+    ws = Connect(url, &result, std::string());
     ASSERT_TRUE(ws);
     ASSERT_EQ(PP_OK, result);
     for (int i = 0; i <= trial_count; ++i) {
@@ -1060,7 +1065,7 @@ std::string TestWebSocket::TestAbortReceiveMessageCall() {
   }
   // Same test, but the last receiving message is large message over 64KiB.
   for (int trial = 1; trial <= trial_count; trial++) {
-    ws = Connect(url, &result, "");
+    ws = Connect(url, &result, std::string());
     ASSERT_TRUE(ws);
     ASSERT_EQ(PP_OK, result);
     for (int i = 0; i <= trial_count; ++i) {
@@ -1102,12 +1107,12 @@ std::string TestWebSocket::TestCcInterfaces() {
   // Check uninitialized properties access.
   ASSERT_EQ(0, ws.GetBufferedAmount());
   ASSERT_EQ(0, ws.GetCloseCode());
-  ASSERT_TRUE(AreEqualWithString(ws.GetCloseReason().pp_var(), ""));
+  ASSERT_TRUE(AreEqualWithString(ws.GetCloseReason().pp_var(), std::string()));
   ASSERT_EQ(false, ws.GetCloseWasClean());
-  ASSERT_TRUE(AreEqualWithString(ws.GetExtensions().pp_var(), ""));
-  ASSERT_TRUE(AreEqualWithString(ws.GetProtocol().pp_var(), ""));
+  ASSERT_TRUE(AreEqualWithString(ws.GetExtensions().pp_var(), std::string()));
+  ASSERT_TRUE(AreEqualWithString(ws.GetProtocol().pp_var(), std::string()));
   ASSERT_EQ(PP_WEBSOCKETREADYSTATE_INVALID, ws.GetReadyState());
-  ASSERT_TRUE(AreEqualWithString(ws.GetURL().pp_var(), ""));
+  ASSERT_TRUE(AreEqualWithString(ws.GetURL().pp_var(), std::string()));
 
   // Check communication interfaces (connect, send, receive, and close).
   TestCompletionCallback connect_callback(
@@ -1163,7 +1168,7 @@ std::string TestWebSocket::TestCcInterfaces() {
   ASSERT_TRUE(
       AreEqualWithString(ws.GetCloseReason().pp_var(), reason.c_str()));
   ASSERT_EQ(true, ws.GetCloseWasClean());
-  ASSERT_TRUE(AreEqualWithString(ws.GetProtocol().pp_var(), ""));
+  ASSERT_TRUE(AreEqualWithString(ws.GetProtocol().pp_var(), std::string()));
   ASSERT_EQ(PP_WEBSOCKETREADYSTATE_CLOSED, ws.GetReadyState());
   ASSERT_TRUE(AreEqualWithString(
       ws.GetURL().pp_var(), GetFullURL(kCloseServerURL).c_str()));
@@ -1268,7 +1273,8 @@ std::string TestWebSocket::TestUtilityValidConnect() {
   const std::vector<WebSocketEvent>& events = websocket.GetSeenEvents();
   ASSERT_EQ(1U, events.size());
   ASSERT_EQ(WebSocketEvent::EVENT_OPEN, events[0].event_type);
-  ASSERT_TRUE(AreEqualWithString(websocket.GetExtensions().pp_var(), ""));
+  ASSERT_TRUE(
+      AreEqualWithString(websocket.GetExtensions().pp_var(), std::string()));
 
   PASS();
 }
@@ -1496,7 +1502,7 @@ std::string TestWebSocket::TestUtilityBufferedAmount() {
 
   // After connection closure, all sending requests fail and just increase
   // the bufferedAmount property.
-  result = websocket.Send(pp::Var(std::string("")));
+  result = websocket.Send(pp::Var(std::string()));
   ASSERT_EQ(PP_ERROR_FAILED, result);
   buffered_amount = websocket.GetBufferedAmount();
   ASSERT_EQ(base_buffered_amount + kMessageFrameOverhead, buffered_amount);
diff --git a/ppapi/tests/test_x509_certificate_private.cc b/ppapi/tests/test_x509_certificate_private.cc
index 6aee30f..fab2f21 100644
--- a/ppapi/tests/test_x509_certificate_private.cc
+++ b/ppapi/tests/test_x509_certificate_private.cc
@@ -166,22 +166,30 @@ std::string TestX509CertificatePrivate::TestValidCertificate() {
       PP_X509CERTIFICATE_PRIVATE_SUBJECT_COUNTRY_NAME, "US"));
   ASSERT_TRUE(FieldMatchesString(certificate,
       PP_X509CERTIFICATE_PRIVATE_SUBJECT_ORGANIZATION_NAME, "Google Inc"));
-  ASSERT_TRUE(FieldMatchesString(certificate,
-      PP_X509CERTIFICATE_PRIVATE_SUBJECT_ORGANIZATION_UNIT_NAME, ""));
+  ASSERT_TRUE(FieldMatchesString(
+      certificate,
+      PP_X509CERTIFICATE_PRIVATE_SUBJECT_ORGANIZATION_UNIT_NAME,
+      std::string()));
 
   ASSERT_TRUE(FieldMatchesString(certificate,
       PP_X509CERTIFICATE_PRIVATE_ISSUER_COMMON_NAME, "Thawte SGC CA"));
-  ASSERT_TRUE(FieldMatchesString(certificate,
-      PP_X509CERTIFICATE_PRIVATE_ISSUER_LOCALITY_NAME, ""));
-  ASSERT_TRUE(FieldMatchesString(certificate,
-      PP_X509CERTIFICATE_PRIVATE_ISSUER_STATE_OR_PROVINCE_NAME, ""));
-  ASSERT_TRUE(FieldMatchesString(certificate,
-      PP_X509CERTIFICATE_PRIVATE_ISSUER_COUNTRY_NAME, "ZA"));
+  ASSERT_TRUE(
+      FieldMatchesString(certificate,
+                         PP_X509CERTIFICATE_PRIVATE_ISSUER_LOCALITY_NAME,
+                         std::string()));
+  ASSERT_TRUE(FieldMatchesString(
+      certificate,
+      PP_X509CERTIFICATE_PRIVATE_ISSUER_STATE_OR_PROVINCE_NAME,
+      std::string()));
+  ASSERT_TRUE(FieldMatchesString(
+      certificate, PP_X509CERTIFICATE_PRIVATE_ISSUER_COUNTRY_NAME, "ZA"));
   ASSERT_TRUE(FieldMatchesString(certificate,
       PP_X509CERTIFICATE_PRIVATE_ISSUER_ORGANIZATION_NAME,
       "Thawte Consulting (Pty) Ltd."));
-  ASSERT_TRUE(FieldMatchesString(certificate,
-      PP_X509CERTIFICATE_PRIVATE_ISSUER_ORGANIZATION_UNIT_NAME, ""));
+  ASSERT_TRUE(FieldMatchesString(
+      certificate,
+      PP_X509CERTIFICATE_PRIVATE_ISSUER_ORGANIZATION_UNIT_NAME,
+      std::string()));
 
   ASSERT_FALSE(FieldIsNull(certificate,
       PP_X509CERTIFICATE_PRIVATE_SERIAL_NUMBER));