Introduce intrinsic to expose debug state to generated code.

src/assembler.cc

Index: src/assembler.cc
diff --git a/src/assembler.cc b/src/assembler.cc
index e8fa728797372cc7ed3f100adec760a2d13c9a4c..d1c38e72bb3d4d8c7e67dd7d7ebd933e253ea19b 100644
--- a/src/assembler.cc
+++ b/src/assembler.cc
@@ -1428,6 +1428,12 @@ ExternalReference ExternalReference::cpu_features() {
 }
 
 
+ExternalReference ExternalReference::debug_is_active_address(
+    Isolate* isolate) {
+  return ExternalReference(isolate->debug()->is_active_address());
+}
+
+
 ExternalReference ExternalReference::debug_after_break_target_address(
     Isolate* isolate) {
   return ExternalReference(isolate->debug()->after_break_target_address());