Re-land FastAccessorBuilder.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 70bc0444b75dc1c4643bb6dc8fb8fe1f128bc397..0e444e0cf8c7c2540f2d8cff28abc9d9bb9a15cd 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -596,6 +596,7 @@ source_set("v8_base") {
 
   sources = [
     "include/v8-debug.h",
+    "include/v8-experimental.h",
     "include/v8-platform.h",
     "include/v8-profiler.h",
     "include/v8-testing.h",
@@ -613,6 +614,8 @@ source_set("v8_base") {
     "src/allocation-site-scopes.h",
     "src/api.cc",
     "src/api.h",
+    "src/api-experimental.cc",
+    "src/api-experimental.h",
     "src/api-natives.cc",
     "src/api-natives.h",
     "src/arguments.cc",
@@ -724,6 +727,8 @@ source_set("v8_base") {
     "src/compiler/escape-analysis.h",
     "src/compiler/escape-analysis-reducer.cc",
     "src/compiler/escape-analysis-reducer.h",
+    "src/compiler/fast-accessor-assembler.cc",
+    "src/compiler/fast-accessor-assembler.h",
     "src/compiler/frame.cc",
     "src/compiler/frame.h",
     "src/compiler/frame-elider.cc",