Add v8_enable_verify_predictable gn args (mirroring the gyp var)

BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/android/config.gni")
 import("//build/config/arm.gni")
 import("//build/config/dcheck_always_on.gni")
 import("//build/config/mips.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
 
 import("gni/v8.gni")
 import("gni/isolate.gni")
 import("snapshot_toolchain.gni")
 
 declare_args() {
   # Print to stdout on Android.
   v8_android_log_stdout = false
 
   # Sets -DVERIFY_HEAP.
   v8_enable_verify_heap = false
 
+  # Sets -DVERIFY_PREDICTABLE
+  v8_enable_verify_predictable = false
+
   # Enable compiler warnings when using V8_DEPRECATED apis.
   v8_deprecation_warnings = false
 
   # Enable compiler warnings when using V8_DEPRECATE_SOON apis.
   v8_imminent_deprecation_warnings = ""
 
   # Embeds the given script into the snapshot.
   v8_embed_script = ""
 
   # Sets -dENABLE_DISASSEMBLER.
@@ skipping 140 matching lines @@
   }
   if (v8_enable_gdbjit) {
     defines += [ "ENABLE_GDB_JIT_INTERFACE" ]
   }
   if (v8_object_print) {
     defines += [ "OBJECT_PRINT" ]
   }
   if (v8_enable_verify_heap) {
     defines += [ "VERIFY_HEAP" ]
   }
+  if (v8_enable_verify_predictable) {
+    defines += [ "VERIFY_PREDICTABLE" ]
+  }
   if (v8_interpreted_regexp) {
     defines += [ "V8_INTERPRETED_REGEXP" ]
   }
   if (v8_deprecation_warnings) {
     defines += [ "V8_DEPRECATION_WARNINGS" ]
   }
   if (v8_imminent_deprecation_warnings) {
     defines += [ "V8_IMMINENT_DEPRECATION_WARNINGS" ]
   }
   if (v8_enable_i18n_support) {
@@ skipping 2810 matching lines @@
   ]
 
   configs = [
     ":external_config",
     ":internal_config_base",
   ]
 }
 
 v8_fuzzer("wasm_data_section_fuzzer") {
 }