X64: Fixups in heap-test.cc to make it compile in X64 mode.

src/x64/assembler-x64.cc

Index: src/x64/assembler-x64.cc
diff --git a/src/x64/assembler-x64.cc b/src/x64/assembler-x64.cc
index 0efb34a841b7bc2fe281715983fbb01f02762057..fb3bce2383dde74534f08648d540f98177d197ff 100644
--- a/src/x64/assembler-x64.cc
+++ b/src/x64/assembler-x64.cc
@@ -105,6 +105,12 @@ Assembler::~Assembler()  {
   UNIMPLEMENTED();
 }
 
+
+void Assembler::nop() {
+  UNIMPLEMENTED();
+}
+
+
 void BreakLocationIterator::ClearDebugBreakAtReturn() {
   UNIMPLEMENTED();
 }
@@ -352,6 +358,12 @@ void CpuFeatures::Probe()  {
   UNIMPLEMENTED();
 }
 
+
+bool Debug::IsDebugBreakAtReturn(v8::internal::RelocInfo*) {
+  UNIMPLEMENTED();
+  return false;
+}
+
 void Debug::GenerateCallICDebugBreak(MacroAssembler* a) {
   UNIMPLEMENTED();
 }