Set the code age field of SharedFunctionInfo correctly.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 9da480ea743a6df283a4228a51669acccafa37ad..f3a7fd3ce72bf9feeeba4c58f0fd4280abde914b 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -3667,8 +3667,8 @@ int SharedFunctionInfo::code_age() {
 
 
 void SharedFunctionInfo::set_code_age(int code_age) {
-  set_compiler_hints(compiler_hints() |
-                     ((code_age & kCodeAgeMask) << kCodeAgeShift));
+  int hints = compiler_hints() & ~(kCodeAgeMask << kCodeAgeShift);
+  set_compiler_hints(hints | ((code_age & kCodeAgeMask) << kCodeAgeShift));
 }