Add support for enabling DCHECKs in release mode

src/assembler.cc

Index: src/assembler.cc
diff --git a/src/assembler.cc b/src/assembler.cc
index c73b470c28cb47592e502879253901488ce9483f..78ea639bcbd7dde3858dc6ff32e92497076cab21 100644
--- a/src/assembler.cc
+++ b/src/assembler.cc
@@ -177,7 +177,7 @@ PredictableCodeSizeScope::~PredictableCodeSizeScope() {
 // -----------------------------------------------------------------------------
 // Implementation of CpuFeatureScope
 
-#ifdef DEBUG
+#if DCHECK_IS_ON
 CpuFeatureScope::CpuFeatureScope(AssemblerBase* assembler, CpuFeature f)
     : assembler_(assembler) {
   DCHECK(CpuFeatures::IsSupported(f));
@@ -289,7 +289,7 @@ int Label::pos() const {
 //                dropped, and last non-zero chunk tagged with 1.)
 
 
-#ifdef DEBUG
+#if DCHECK_IS_ON
 const int kMaxStandardNonCompactModes = 14;
 #endif
 
@@ -408,7 +408,7 @@ void RelocInfoWriter::WriteExtraTaggedData(intptr_t data_delta, int top_tag) {
 
 
 void RelocInfoWriter::Write(const RelocInfo* rinfo) {
-#ifdef DEBUG
+#if DCHECK_IS_ON
   byte* begin_pos = pos_;
 #endif
   DCHECK(rinfo->rmode() < RelocInfo::NUMBER_OF_MODES);
@@ -474,7 +474,7 @@ void RelocInfoWriter::Write(const RelocInfo* rinfo) {
     WriteExtraTaggedPC(pc_delta, saved_mode);
   }
   last_pc_ = rinfo->pc();
-#ifdef DEBUG
+#if DCHECK_IS_ON
   DCHECK(begin_pos - pos_ <= kMaxSize);
 #endif
 }
@@ -732,7 +732,7 @@ RelocIterator::RelocIterator(const CodeDesc& desc, int mode_mask) {
 // Implementation of RelocInfo
 
 
-#ifdef DEBUG
+#if DCHECK_IS_ON
 bool RelocInfo::RequiresRelocation(const CodeDesc& desc) {
   // Ensure there are no code targets or embedded objects present in the
   // deoptimization entries, they would require relocation after code