Revert of [fullcodegen] Remove the hacky %_FastOneByteArrayJoin intrinsic.

src/crankshaft/hydrogen.cc

Index: src/crankshaft/hydrogen.cc
diff --git a/src/crankshaft/hydrogen.cc b/src/crankshaft/hydrogen.cc
index d0e298c248702475b7abf28345293f707be793d8..273ff52684d683191c87efded6b362a7ce840b99 100644
--- a/src/crankshaft/hydrogen.cc
+++ b/src/crankshaft/hydrogen.cc
@@ -12885,6 +12885,16 @@
 }
 
 
+void HOptimizedGraphBuilder::GenerateFastOneByteArrayJoin(CallRuntime* call) {
+  // Simply returning undefined here would be semantically correct and even
+  // avoid the bailout. Nevertheless, some ancient benchmarks like SunSpider's
+  // string-fasta would tank, because fullcode contains an optimized version.
+  // Obviously the fullcode => Crankshaft => bailout => fullcode dance is
+  // faster... *sigh*
+  return Bailout(kInlinedRuntimeFunctionFastOneByteArrayJoin);
+}
+
+
 void HOptimizedGraphBuilder::GenerateDebugBreakInOptimizedCode(
     CallRuntime* call) {
   Add<HDebugBreak>();