[debugger] remove debugger statement support from FCG/CS.

src/compiler/ast-graph-builder.cc

Index: src/compiler/ast-graph-builder.cc
diff --git a/src/compiler/ast-graph-builder.cc b/src/compiler/ast-graph-builder.cc
index 3aefd2a60140ee459d04e31a0faf72f81827dd94..e199a032a8f74faabfb2b502c0e8f9e7df47f19d 100644
--- a/src/compiler/ast-graph-builder.cc
+++ b/src/compiler/ast-graph-builder.cc
@@ -1197,9 +1197,8 @@ void AstGraphBuilder::VisitTryFinallyStatement(TryFinallyStatement* stmt) {
 
 
 void AstGraphBuilder::VisitDebuggerStatement(DebuggerStatement* stmt) {
-  Node* node = NewNode(javascript()->Debugger());
-  PrepareFrameState(node, stmt->DebugBreakId());
-  environment()->MarkAllLocalsLive();
+  // Debugger statement is supported only by going through Ignition first.
+  UNREACHABLE();
 }