[Support] Add TimeTraceScope constructor without detail arg

This simplifies code where no extra details are required
Also don't write out detail when it is empty.

Differential Revision: https://reviews.llvm.org/D71347
diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index a226166..c54d15d 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -896,7 +896,7 @@
 
   {
     PrettyStackTraceString CrashInfo("Per-function optimization");
-    llvm::TimeTraceScope TimeScope("PerFunctionPasses", StringRef(""));
+    llvm::TimeTraceScope TimeScope("PerFunctionPasses");
 
     PerFunctionPasses.doInitialization();
     for (Function &F : *TheModule)
@@ -907,13 +907,13 @@
 
   {
     PrettyStackTraceString CrashInfo("Per-module optimization passes");
-    llvm::TimeTraceScope TimeScope("PerModulePasses", StringRef(""));
+    llvm::TimeTraceScope TimeScope("PerModulePasses");
     PerModulePasses.run(*TheModule);
   }
 
   {
     PrettyStackTraceString CrashInfo("Code generation");
-    llvm::TimeTraceScope TimeScope("CodeGenPasses", StringRef(""));
+    llvm::TimeTraceScope TimeScope("CodeGenPasses");
     CodeGenPasses.run(*TheModule);
   }
 
@@ -1499,7 +1499,7 @@
                               BackendAction Action,
                               std::unique_ptr<raw_pwrite_stream> OS) {
 
-  llvm::TimeTraceScope TimeScope("Backend", StringRef(""));
+  llvm::TimeTraceScope TimeScope("Backend");
 
   std::unique_ptr<llvm::Module> EmptyModule;
   if (!CGOpts.ThinLTOIndexFile.empty()) {
diff --git a/clang/lib/CodeGen/CodeGenAction.cpp b/clang/lib/CodeGen/CodeGenAction.cpp
index 1fa1f62..7f3f358 100644
--- a/clang/lib/CodeGen/CodeGenAction.cpp
+++ b/clang/lib/CodeGen/CodeGenAction.cpp
@@ -249,7 +249,7 @@
 
     void HandleTranslationUnit(ASTContext &C) override {
       {
-        llvm::TimeTraceScope TimeScope("Frontend", StringRef(""));
+        llvm::TimeTraceScope TimeScope("Frontend");
         PrettyStackTraceString CrashInfo("Per-file LLVM IR generation");
         if (FrontendTimesIsEnabled) {
           LLVMIRGenerationRefCount += 1;