Update V8 to r6238 as required by WebKit r75993

Change-Id: I12f638fcdd02d9102abab17d81c23cde63c08f22
diff --git a/src/v8-counters.h b/src/v8-counters.h
index fa5d581..aa30e4e 100644
--- a/src/v8-counters.h
+++ b/src/v8-counters.h
@@ -249,15 +249,7 @@
   SC(smi_checks_removed, V8.SmiChecksRemoved)                         \
   SC(map_checks_removed, V8.MapChecksRemoved)                         \
   SC(quote_json_char_count, V8.QuoteJsonCharacterCount)               \
-  SC(quote_json_char_recount, V8.QuoteJsonCharacterReCount)           \
-  SC(instance_of, V8.InstanceOf)                                      \
-  SC(instance_of_cache, V8.InstanceOfCache)                           \
-  SC(instance_of_stub_true, V8.InstanceOfStubTrue)                    \
-  SC(instance_of_stub_false, V8.InstanceOfStubFalse)                  \
-  SC(instance_of_stub_false_null, V8.InstanceOfStubFalseNull)         \
-  SC(instance_of_stub_false_string, V8.InstanceOfStubFalseString)     \
-  SC(instance_of_full, V8.InstanceOfFull)                             \
-  SC(instance_of_slow, V8.InstanceOfSlow)
+  SC(quote_json_char_recount, V8.QuoteJsonCharacterReCount)
 
 
 // This file contains all the v8 counters that are in use.