[CodeGen] Modernize InstrProfStats (NFC)

Author: kazutakahirata

clang/lib/CodeGen/CodeGenModule.h

@@ -214,16 +214,14 @@ struct ObjCEntrypoints {
 
 /// This class records statistics on instrumentation based profiling.
 class InstrProfStats {
-  uint32_t VisitedInMainFile;
-  uint32_t MissingInMainFile;
-  uint32_t Visited;
-  uint32_t Missing;
-  uint32_t Mismatched;
+  uint32_t VisitedInMainFile = 0;
+  uint32_t MissingInMainFile = 0;
+  uint32_t Visited = 0;
+  uint32_t Missing = 0;
+  uint32_t Mismatched = 0;
 
 public:
-  InstrProfStats()
-      : VisitedInMainFile(0), MissingInMainFile(0), Visited(0), Missing(0),
-        Mismatched(0) {}
+  InstrProfStats() = default;
   /// Record that we've visited a function and whether or not that function was
   /// in the main source file.
   void addVisited(bool MainFile) {