Allow inlining of native functions. Fix performance degradation (more investigation to follow).

runtime/vm/flow_graph_inliner.cc

Index: runtime/vm/flow_graph_inliner.cc
diff --git a/runtime/vm/flow_graph_inliner.cc b/runtime/vm/flow_graph_inliner.cc
index 950a15d70196f16770eb0f9bd881bd48df6b6e67..930da8dd41c235c664bacb15c141b9c091d91138 100644
--- a/runtime/vm/flow_graph_inliner.cc
+++ b/runtime/vm/flow_graph_inliner.cc
@@ -614,9 +614,6 @@ class CallSiteInliner : public ValueObject {
   bool TryInlining(const Function& function,
                    const Array& argument_names,
                    InlinedCallData* call_data) {
-    if (function.is_native()) {
-      return false;
-    }
     TRACE_INLINING(THR_Print("  => %s (deopt count %d)\n",
                              function.ToCString(),
                              function.deoptimization_counter()));
@@ -1388,9 +1385,6 @@ bool PolymorphicInliner::CheckNonInlinedDuplicate(const Function& target) {
 
 bool PolymorphicInliner::TryInliningPoly(intptr_t receiver_cid,
                                         const Function& target) {
-  if (target.is_native()) {

[Florian Schneider, 2015/11/03 18:34:18]

Yes, we want to inline recognized methods. The flow graph builder bails out of
inlining non-recognized natives already in VisitNativeBodyNode.

-    return false;
-  }
   if (TryInlineRecognizedMethod(receiver_cid, target)) {
     owner_->inlined_ = true;
     return true;