Remove special debug ExternalReferences.

src/assembler.cc

Index: src/assembler.cc
diff --git a/src/assembler.cc b/src/assembler.cc
index 103ca139f523a7f2becd3a066ab570b157f19fd8..64e61b85987ebd39c7f0f4603e6c947e9601b4c7 100644
--- a/src/assembler.cc
+++ b/src/assembler.cc
@@ -996,9 +996,6 @@ ExternalReference::ExternalReference(const IC_Utility& ic_utility,
                                      Isolate* isolate)
   : address_(Redirect(isolate, ic_utility.address())) {}
 
-ExternalReference::ExternalReference(const Debug_Address& debug_address,
-                                     Isolate* isolate)
-  : address_(debug_address.address(isolate)) {}
 
 ExternalReference::ExternalReference(StatsCounter* counter)
   : address_(reinterpret_cast<Address>(counter->GetInternalPointer())) {}
@@ -1431,6 +1428,20 @@ ExternalReference ExternalReference::cpu_features() {
 }
 
 
+ExternalReference ExternalReference::debug_after_break_target_address(
+    Isolate* isolate) {
+  return ExternalReference(isolate->debug()->after_break_target_address());
+}
+
+
+ExternalReference
+    ExternalReference::debug_restarter_frame_function_pointer_address(
+        Isolate* isolate) {
+  return ExternalReference(
+      isolate->debug()->restarter_frame_function_pointer_address());
+}
+
+
 double power_helper(double x, double y) {
   int y_int = static_cast<int>(y);
   if (y == y_int) {