Compile V8 with extra optimization in GN Release mode.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 5c14eac6891c1bf6157b4722e85b4a0cf7550227..4c3f8c12f3b73bd2fb4fc149124f58368f87b303 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1126,6 +1126,11 @@ source_set("v8_base") {
   configs += [ "//build/config/compiler:no_chromium_code" ]
   configs += [ ":internal_config", ":features", ":toolchain" ]
 
+  if (!is_debug) {
+    configs -= [ "//build/config/compiler:optimize" ]
+    configs += [ "//build/config/compiler:optimize_max" ]
+  }
+
   defines = []
   deps = [ ":v8_libbase" ]
 
@@ -1211,6 +1216,11 @@ source_set("v8_libbase") {
   configs += [ "//build/config/compiler:no_chromium_code" ]
   configs += [ ":internal_config_base", ":features", ":toolchain" ]
 
+  if (!is_debug) {
+    configs -= [ "//build/config/compiler:optimize" ]
+    configs += [ "//build/config/compiler:optimize_max" ]
+  }
+
   defines = []
 
   if (is_posix) {
@@ -1274,6 +1284,11 @@ source_set("v8_libplatform") {
   configs += [ "//build/config/compiler:no_chromium_code" ]
   configs += [ ":internal_config_base", ":features", ":toolchain" ]
 
+  if (!is_debug) {
+    configs -= [ "//build/config/compiler:optimize" ]
+    configs += [ "//build/config/compiler:optimize_max" ]
+  }
+
   deps = [
     ":v8_libbase",
   ]