Don't need to stabilize mRefCnt to 1 in nsStyleContext dtor (bug 196956). r/sr=dbaron.

content/shared/public/nsStyleContext.h

@@ -66,7 +66,6 @@ public:
     --mRefCnt;
     NS_LOG_RELEASE(this, mRefCnt, "nsStyleContext");
     if (mRefCnt == 0) {
-      mRefCnt = 1;
       Destroy();
       return 0;
     }

layout/style/nsStyleContext.h

@@ -66,7 +66,6 @@ public:
     --mRefCnt;
     NS_LOG_RELEASE(this, mRefCnt, "nsStyleContext");
     if (mRefCnt == 0) {
-      mRefCnt = 1;
       Destroy();
       return 0;
     }