Simplify and fix code aging.

src/x64/codegen-x64.cc

Index: src/x64/codegen-x64.cc
diff --git a/src/x64/codegen-x64.cc b/src/x64/codegen-x64.cc
index e2471e69cc726d69c1eed338ac333558a8be6b9f..67d1d90b6c09fa4d52be6d01c8e640d051b8c2c3 100644
--- a/src/x64/codegen-x64.cc
+++ b/src/x64/codegen-x64.cc
@@ -681,28 +681,6 @@ static byte* GetNoCodeAgeSequence(uint32_t* length) {
 }
 
 
-byte* Code::FindPlatformCodeAgeSequence() {
-  byte* start = instruction_start();
-  uint32_t young_length;
-  byte* young_sequence = GetNoCodeAgeSequence(&young_length);
-  if (!memcmp(start, young_sequence, young_length) ||
-      *start == kCallOpcode) {
-    return start;
-  } else {
-    byte* start_after_strict = NULL;
-    if (kind() == FUNCTION) {
-      start_after_strict = start + kSizeOfFullCodegenStrictModePrologue;
-    } else {
-      ASSERT(kind() == OPTIMIZED_FUNCTION);
-      start_after_strict = start + kSizeOfOptimizedStrictModePrologue;
-    }
-    ASSERT(!memcmp(start_after_strict, young_sequence, young_length) ||
-           *start_after_strict == kCallOpcode);
-    return start_after_strict;
-  }
-}
-
-
 bool Code::IsYoungSequence(byte* sequence) {
   uint32_t young_length;
   byte* young_sequence = GetNoCodeAgeSequence(&young_length);