[interpreter] Add basic framework for bytecode handler code generation.

src/flag-definitions.h

Index: src/flag-definitions.h
diff --git a/src/flag-definitions.h b/src/flag-definitions.h
index bbffaa8a72973ec2d55ffbe3064f2c03c81e6b87..17d824f2693cd8d373c3d38f134c55da73b72229 100644
--- a/src/flag-definitions.h
+++ b/src/flag-definitions.h
@@ -269,7 +269,7 @@ DEFINE_BOOL(smi_binop, true, "support smi representation in binary operations")
 // Flags for optimization types.
 DEFINE_BOOL(optimize_for_size, false,
             "Enables optimizations which favor memory size over execution "
-            "speed.")
+            "speed")
 
 DEFINE_VALUE_IMPLICATION(optimize_for_size, max_semi_space_size, 1)
 
@@ -277,6 +277,12 @@ DEFINE_VALUE_IMPLICATION(optimize_for_size, max_semi_space_size, 1)
 DEFINE_BOOL(unbox_double_arrays, true, "automatically unbox arrays of doubles")
 DEFINE_BOOL(string_slices, true, "use string slices")
 
+// Flags for Ignition.
+DEFINE_BOOL(ignition, false, "use ignition interpreter")
+DEFINE_STRING(ignition_filter, "~~", "filter for ignition interpreter")
+DEFINE_BOOL(trace_ignition_codegen, false,
+            "trace the codegen of ignition interpreter bytecode handlers")
+
 // Flags for Crankshaft.
 DEFINE_BOOL(crankshaft, true, "use crankshaft")
 DEFINE_STRING(hydrogen_filter, "*", "optimization filter")