Introduce intrinsic to expose debug state to generated code.

src/arm64/full-codegen-arm64.cc

Index: src/arm64/full-codegen-arm64.cc
diff --git a/src/arm64/full-codegen-arm64.cc b/src/arm64/full-codegen-arm64.cc
index ba3b5d086e6a515f24d7c8e012707dcd181eb9ea..928a2385e9e6b8f6cbafbd9b10d9e6dfa2c8cfaf 100644
--- a/src/arm64/full-codegen-arm64.cc
+++ b/src/arm64/full-codegen-arm64.cc
@@ -3738,6 +3738,17 @@ void FullCodeGenerator::EmitFastAsciiArrayJoin(CallRuntime* expr) {
 }
 
 
+void FullCodeGenerator::EmitDebugIsActive(CallRuntime* expr) {
+  ASSERT(expr->arguments()->length() == 0);
+  ExternalReference debug_is_active =
+      ExternalReference::debug_is_active_address(isolate());
+  __ Mov(x10, debug_is_active);
+  __ Ldrb(x0, MemOperand(x10));
+  __ SmiTag(x0);
+  context()->Plug(x0);
+}
+
+
 void FullCodeGenerator::VisitCallRuntime(CallRuntime* expr) {
   if (expr->function() != NULL &&
       expr->function()->intrinsic_type == Runtime::INLINE) {