ART: Refactor jmethodID handling

ArtMethod objects have been native since Marshmallow.
Remove the dependency on being runnable. Refactor the
code into the jni_internal header.

Test: m test-art-host
Change-Id: I1385fcd4c08981491701da55a87036b447aa2fc2
diff --git a/runtime/reflection.cc b/runtime/reflection.cc
index f88309b..3128380 100644
--- a/runtime/reflection.cc
+++ b/runtime/reflection.cc
@@ -453,7 +453,7 @@
     return JValue();
   }
 
-  ArtMethod* method = soa.DecodeMethod(mid);
+  ArtMethod* method = jni::DecodeArtMethod(mid);
   bool is_string_init = method->GetDeclaringClass()->IsStringClass() && method->IsConstructor();
   if (is_string_init) {
     // Replace calls to String.<init> with equivalent StringFactory call.
@@ -484,7 +484,7 @@
     return JValue();
   }
 
-  ArtMethod* method = soa.DecodeMethod(mid);
+  ArtMethod* method = jni::DecodeArtMethod(mid);
   bool is_string_init = method->GetDeclaringClass()->IsStringClass() && method->IsConstructor();
   if (is_string_init) {
     // Replace calls to String.<init> with equivalent StringFactory call.
@@ -516,7 +516,7 @@
   }
 
   ObjPtr<mirror::Object> receiver = soa.Decode<mirror::Object>(obj);
-  ArtMethod* method = FindVirtualMethod(receiver, soa.DecodeMethod(mid));
+  ArtMethod* method = FindVirtualMethod(receiver, jni::DecodeArtMethod(mid));
   bool is_string_init = method->GetDeclaringClass()->IsStringClass() && method->IsConstructor();
   if (is_string_init) {
     // Replace calls to String.<init> with equivalent StringFactory call.
@@ -548,7 +548,7 @@
   }
 
   ObjPtr<mirror::Object> receiver = soa.Decode<mirror::Object>(obj);
-  ArtMethod* method = FindVirtualMethod(receiver, soa.DecodeMethod(mid));
+  ArtMethod* method = FindVirtualMethod(receiver, jni::DecodeArtMethod(mid));
   bool is_string_init = method->GetDeclaringClass()->IsStringClass() && method->IsConstructor();
   if (is_string_init) {
     // Replace calls to String.<init> with equivalent StringFactory call.
@@ -739,8 +739,11 @@
     arg_array.Append(value.GetI());
   }
 
-  soa.DecodeMethod(m)->Invoke(soa.Self(), arg_array.GetArray(), arg_array.GetNumBytes(),
-                              &result, shorty);
+  jni::DecodeArtMethod(m)->Invoke(soa.Self(),
+                                  arg_array.GetArray(),
+                                  arg_array.GetNumBytes(),
+                                  &result,
+                                  shorty);
   return result.GetL();
 }