Split ScarinessScore between its "storage" (POD), and an initializing object.

[filcab]

Summary

This is needed so we can use it for D23672 on VS2013, since this VS
version doesn't support unrestricted unions, and doesn't allow us to
uses an object without a trivial default constructor inside a union.

[filcab]

Updated to account for D24029.
Kostya: I know you've accepted the revision, but since this is a non-trivial change, I'm updating it to show why D24029 would help.

[filcab]

Merged two commits by mistake.

[kcc]

LGTM

lib/asan/asan_scariness_score.h

 #ifndef ASAN_SCARINESS_SCORE_H
 #define ASAN_SCARINESS_SCORE_H
 
 #include "asan_flags.h"
 #include "sanitizer_common/sanitizer_common.h"
 #include "sanitizer_common/sanitizer_libc.h"
 
 namespace __asan {
-class ScarinessScore {
- public:
-  ScarinessScore() {
+struct ScarinessScoreBase {
+  void Clear() {
     descr[0] = 0;
+    score = 0;
   }
   void Scare(int add_to_score, const char *reason) {
     if (descr[0])
       internal_strlcat(descr, "-", sizeof(descr));
     internal_strlcat(descr, reason, sizeof(descr));
     score += add_to_score;
   };
   int GetScore() const { return score; }
   const char *GetDescription() const { return descr; }
   void Print() {
     if (score && flags()->print_scariness)
       Printf("SCARINESS: %d (%s)\n", score, descr);
   }
   static void PrintSimple(int score, const char *descr) {
-    ScarinessScore SS;
-    SS.Scare(score, descr);
-    SS.Print();
+    ScarinessScoreBase SSB;
+    SSB.Clear();
+    SSB.Scare(score, descr);
+    SSB.Print();
   }
 
  private:
-  int score = 0;
+  int score;
   char descr[1024];
 };
 
+struct ScarinessScore : ScarinessScoreBase {
+  ScarinessScore() {
+    Clear();
+  }
+};
+
 }  // namespace __asan
 
 #endif  // ASAN_SCARINESS_SCORE_H