Rewrite std::string("") to std::string(), Linux edition.

base/debug/trace_event_unittest.cc

Index: base/debug/trace_event_unittest.cc
diff --git a/base/debug/trace_event_unittest.cc b/base/debug/trace_event_unittest.cc
index 8376660300d2d0bc2a9dc8bb0934e178021c93f7..782f07bdf40812c4a7598a08ece04b4f335ce8d4 100644
--- a/base/debug/trace_event_unittest.cc
+++ b/base/debug/trace_event_unittest.cc
@@ -1535,7 +1535,7 @@ TEST_F(TraceEventTestFixture, TraceCategoriesAfterNestedEnable) {
   trace_log->SetEnabled(std::string("foo2"), TraceLog::RECORD_UNTIL_FULL);
   EXPECT_TRUE(*trace_log->GetCategoryEnabled("foo2"));
   EXPECT_FALSE(*trace_log->GetCategoryEnabled("baz"));
-  trace_log->SetEnabled(std::string(""), TraceLog::RECORD_UNTIL_FULL);
+  trace_log->SetEnabled(std::string(), TraceLog::RECORD_UNTIL_FULL);
   EXPECT_TRUE(*trace_log->GetCategoryEnabled("foo"));
   EXPECT_TRUE(*trace_log->GetCategoryEnabled("baz"));
   trace_log->SetDisabled();
@@ -1558,7 +1558,8 @@ TEST_F(TraceEventTestFixture, TraceCategoriesAfterNestedEnable) {
 TEST_F(TraceEventTestFixture, TraceOptionsParsing) {
   ManualTestSetUp();
 
-  EXPECT_EQ(TraceLog::RECORD_UNTIL_FULL, TraceLog::TraceOptionsFromString(""));
+  EXPECT_EQ(TraceLog::RECORD_UNTIL_FULL,
+            TraceLog::TraceOptionsFromString(std::string()));
 
   EXPECT_EQ(TraceLog::RECORD_UNTIL_FULL,
             TraceLog::TraceOptionsFromString("record-until-full"));