Use a fixed random seed per default.

tools/gyp/v8.gyp

Index: tools/gyp/v8.gyp
diff --git a/tools/gyp/v8.gyp b/tools/gyp/v8.gyp
index 22fcf94566f93c073f89eae287ead198a26521a8..5baa245d5ee105b7a372b118ddd6497a981187ac 100644
--- a/tools/gyp/v8.gyp
+++ b/tools/gyp/v8.gyp
@@ -28,6 +28,7 @@
 {
   'variables': {
     'v8_code': 1,
+    'v8_random_seed%': 314159265,
   },
   'includes': ['../../build/toolchain.gypi', '../../build/features.gypi'],
   'targets': [
@@ -156,6 +157,11 @@
               '--log-snapshot-positions',
               '--logfile', '<(INTERMEDIATE_DIR)/snapshot.log',
             ],
+            'conditions': [
+              ['v8_random_seed!=0', {
+                'mksnapshot_flags': ['--random-seed', '<(v8_random_seed)'],
+              }],
+            ],
           },
           'action': [
             '<@(_inputs)',