Change FieldHelper to use a handle.

Fixed compaction bugs related to FieldHelper::GetType in:
artSet32InstanceFromCode
SetFieldValueImpl
CheckReceiver
Field_set
interpreter::DoFieldPut
MethodVerifier::VerifyISGet
MethodVerifier::VerifyISPut
MethodVerifier::VerifyIGetQuick

Bug: 13077697

Change-Id: I7de9ded2893b5568d43e4daa86fd135bf5508b72
diff --git a/runtime/mirror/class.cc b/runtime/mirror/class.cc
index 4b02c0f..06c2796 100644
--- a/runtime/mirror/class.cc
+++ b/runtime/mirror/class.cc
@@ -517,11 +517,9 @@
 ArtField* Class::FindDeclaredInstanceField(const StringPiece& name, const StringPiece& type) {
   // Is the field in this class?
   // Interfaces are not relevant because they can't contain instance fields.
-  FieldHelper fh;
   for (size_t i = 0; i < NumInstanceFields(); ++i) {
     ArtField* f = GetInstanceField(i);
-    fh.ChangeField(f);
-    if (name == fh.GetName() && type == fh.GetTypeDescriptor()) {
+    if (name == f->GetName() && type == f->GetTypeDescriptor()) {
       return f;
     }
   }
@@ -566,11 +564,9 @@
 
 ArtField* Class::FindDeclaredStaticField(const StringPiece& name, const StringPiece& type) {
   DCHECK(type != NULL);
-  FieldHelper fh;
   for (size_t i = 0; i < NumStaticFields(); ++i) {
     ArtField* f = GetStaticField(i);
-    fh.ChangeField(f);
-    if (name == fh.GetName() && type == fh.GetTypeDescriptor()) {
+    if (name == f->GetName() && type == f->GetTypeDescriptor()) {
       return f;
     }
   }