Add support for enabling DCHECKs in release mode

src/x64/full-codegen-x64.cc

Index: src/x64/full-codegen-x64.cc
diff --git a/src/x64/full-codegen-x64.cc b/src/x64/full-codegen-x64.cc
index 24747ee9e85b11d7e3fed1b50e70db0d2073e9b2..4250dd5140a39bcd502b21e12735521da6e08c3e 100644
--- a/src/x64/full-codegen-x64.cc
+++ b/src/x64/full-codegen-x64.cc
@@ -26,7 +26,7 @@ namespace internal {
 class JumpPatchSite BASE_EMBEDDED {
  public:
   explicit JumpPatchSite(MacroAssembler* masm) : masm_(masm) {
-#ifdef DEBUG
+#if DCHECK_IS_ON
     info_emitted_ = false;
 #endif
   }
@@ -54,7 +54,7 @@ class JumpPatchSite BASE_EMBEDDED {
       int delta_to_patch_site = masm_->SizeOfCodeGeneratedSince(&patch_site_);
       DCHECK(is_uint8(delta_to_patch_site));
       __ testl(rax, Immediate(delta_to_patch_site));
-#ifdef DEBUG
+#if DCHECK_IS_ON
       info_emitted_ = true;
 #endif
     } else {
@@ -73,7 +73,7 @@ class JumpPatchSite BASE_EMBEDDED {
 
   MacroAssembler* masm_;
   Label patch_site_;
-#ifdef DEBUG
+#if DCHECK_IS_ON
   bool info_emitted_;
 #endif
 };
@@ -403,7 +403,7 @@ void FullCodeGenerator::EmitReturnSequence() {
     __ Pop(rax);
     EmitProfilingCounterReset();
     __ bind(&ok);
-#ifdef DEBUG
+#if DCHECK_IS_ON
     // Add a label for checking the size of the code used for returning.
     Label check_exit_codesize;
     masm_->bind(&check_exit_codesize);
@@ -5123,7 +5123,7 @@ FullCodeGenerator::NestedStatement* FullCodeGenerator::TryFinally::Exit(
 static const byte kJnsInstruction = 0x79;
 static const byte kNopByteOne = 0x66;
 static const byte kNopByteTwo = 0x90;
-#ifdef DEBUG
+#if DCHECK_IS_ON
 static const byte kCallInstruction = 0xe8;
 #endif