Vector ICs: gyp flag to run with vector-stores on.

This is so we can build with the flag on in the snapshot.
D8 then needs to be run with --vector-stores.

BUG=
R=machenbach@chromium.org

Review URL: https://codereview.chromium.org/1339593002

Cr-Commit-Position: refs/heads/master@{#30692}

Makefile

@@ -143,6 +143,10 @@ endif
 ifeq ($(deprecationwarnings), on)
   GYPFLAGS += -Dv8_deprecation_warnings=1
 endif
+# vectorstores=on
+ifeq ($(vectorstores), on)
+  GYPFLAGS += -Dv8_vector_stores=1
+endif
 # imminentdeprecationwarnings=on
 ifeq ($(imminentdeprecationwarnings), on)
   GYPFLAGS += -Dv8_imminent_deprecation_warnings=1

tools/gyp/v8.gyp

@@ -30,6 +30,7 @@
     'icu_use_data_file_flag%': 0,
     'v8_code': 1,
     'v8_random_seed%': 314159265,
+    'v8_vector_stores%': 0,
     'embed_script%': "",
     'v8_extra_library_files%': [],
     'v8_experimental_extra_library_files%': [],
@@ -205,6 +206,9 @@
               ['v8_random_seed!=0', {
                 'mksnapshot_flags': ['--random-seed', '<(v8_random_seed)'],
               }],
+              ['v8_vector_stores!=0', {
+                'mksnapshot_flags': ['--vector-stores'],
+              }],
             ],
           },
           'action': [
@@ -307,6 +311,9 @@
                   ['v8_random_seed!=0', {
                     'mksnapshot_flags': ['--random-seed', '<(v8_random_seed)'],
                   }],
+                  ['v8_vector_stores!=0', {
+                    'mksnapshot_flags': ['--vector-stores'],
+                  }],
                 ],
               },
               'conditions': [