[wasm] Change the constant kV8MaxWasmMemoryPages to a command line flag.

src/flag-definitions.h

Index: src/flag-definitions.h
diff --git a/src/flag-definitions.h b/src/flag-definitions.h
index 971e05176e54a943c98dfdd60d28bc17d2b27ec2..423bebf0f70922c1ded524fc921726c41dc42558 100644
--- a/src/flag-definitions.h
+++ b/src/flag-definitions.h
@@ -159,6 +159,7 @@ struct MaybeBoolFlag {
 #define DEFINE_MAYBE_BOOL(nam, cmt) \
   FLAG(MAYBE_BOOL, MaybeBoolFlag, nam, {false COMMA false}, cmt)
 #define DEFINE_INT(nam, def, cmt) FLAG(INT, int, nam, def, cmt)
+#define DEFINE_UINT(nam, def, cmt) FLAG(UINT, unsigned int, nam, def, cmt)
 #define DEFINE_FLOAT(nam, def, cmt) FLAG(FLOAT, double, nam, def, cmt)
 #define DEFINE_STRING(nam, def, cmt) FLAG(STRING, const char*, nam, def, cmt)
 #define DEFINE_ARGS(nam, cmt) FLAG(ARGS, JSArguments, nam, {0 COMMA NULL}, cmt)
@@ -502,6 +503,7 @@ DEFINE_BOOL(wasm_disable_structured_cloning, false,
             "disable WASM structured cloning")
 DEFINE_INT(wasm_num_compilation_tasks, 10,
            "number of parallel compilation tasks for wasm")
+DEFINE_UINT(wasm_max_mem_pages, 16384, "maximum memory size of a wasm instance")
 DEFINE_BOOL(trace_wasm_encoder, false, "trace encoding of wasm code")
 DEFINE_BOOL(trace_wasm_decoder, false, "trace decoding of wasm code")
 DEFINE_BOOL(trace_wasm_decode_time, false, "trace decoding time of wasm code")