Move ArtField to native

Add linear alloc. Moved ArtField to be native object. Changed image
writer to put ArtFields after the mirror section.

Savings:
2MB on low ram devices
4MB on normal devices

Total PSS measurements before (normal N5, 95s after shell start):
Image size: 7729152 bytes
23112 kB: .NonMoving
23212 kB: .NonMoving
22868 kB: .NonMoving
23072 kB: .NonMoving
22836 kB: .NonMoving
19618 kB: .Zygote
19850 kB: .Zygote
19623 kB: .Zygote
19924 kB: .Zygote
19612 kB: .Zygote
Avg: 42745.4 kB

After:
Image size: 7462912 bytes
17440 kB: .NonMoving
16776 kB: .NonMoving
16804 kB: .NonMoving
17812 kB: .NonMoving
16820 kB: .NonMoving
18788 kB: .Zygote
18856 kB: .Zygote
19064 kB: .Zygote
18841 kB: .Zygote
18629 kB: .Zygote
3499 kB: .LinearAlloc
3408 kB: .LinearAlloc
3424 kB: .LinearAlloc
3600 kB: .LinearAlloc
3436 kB: .LinearAlloc
Avg: 39439.4 kB

No reflection performance changes.

Bug: 19264997
Bug: 17643507

Change-Id: I10c73a37913332080aeb978c7c94713bdfe4fe1c
diff --git a/runtime/interpreter/interpreter_common.cc b/runtime/interpreter/interpreter_common.cc
index 375d644..3ae611b 100644
--- a/runtime/interpreter/interpreter_common.cc
+++ b/runtime/interpreter/interpreter_common.cc
@@ -281,11 +281,10 @@
         // object in the destructor.
         Class* field_class;
         {
-          StackHandleScope<3> hs(self);
-          HandleWrapper<mirror::ArtField> h_f(hs.NewHandleWrapper(&f));
+          StackHandleScope<2> hs(self);
           HandleWrapper<mirror::Object> h_reg(hs.NewHandleWrapper(&reg));
           HandleWrapper<mirror::Object> h_obj(hs.NewHandleWrapper(&obj));
-          field_class = h_f->GetType<true>();
+          field_class = f->GetType<true>();
         }
         if (!reg->VerifierInstanceOf(field_class)) {
           // This should never happen.
diff --git a/runtime/interpreter/interpreter_common.h b/runtime/interpreter/interpreter_common.h
index 2f8bf55..0e0d56a 100644
--- a/runtime/interpreter/interpreter_common.h
+++ b/runtime/interpreter/interpreter_common.h
@@ -24,6 +24,7 @@
 #include <iostream>
 #include <sstream>
 
+#include "art_field-inl.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "class_linker-inl.h"
@@ -32,7 +33,6 @@
 #include "dex_instruction-inl.h"
 #include "entrypoints/entrypoint_utils-inl.h"
 #include "handle_scope-inl.h"
-#include "mirror/art_field-inl.h"
 #include "mirror/art_method-inl.h"
 #include "mirror/class-inl.h"
 #include "mirror/object-inl.h"
@@ -41,7 +41,6 @@
 #include "thread.h"
 #include "well_known_classes.h"
 
-using ::art::mirror::ArtField;
 using ::art::mirror::ArtMethod;
 using ::art::mirror::Array;
 using ::art::mirror::BooleanArray;
diff --git a/runtime/interpreter/unstarted_runtime.cc b/runtime/interpreter/unstarted_runtime.cc
index 9af8102..dd8c57b 100644
--- a/runtime/interpreter/unstarted_runtime.cc
+++ b/runtime/interpreter/unstarted_runtime.cc
@@ -208,20 +208,22 @@
   // going the reflective Dex way.
   mirror::Class* klass = shadow_frame->GetVRegReference(arg_offset)->AsClass();
   mirror::String* name2 = shadow_frame->GetVRegReference(arg_offset + 1)->AsString();
-  mirror::ArtField* found = nullptr;
-  mirror::ObjectArray<mirror::ArtField>* fields = klass->GetIFields();
-  for (int32_t i = 0; i < fields->GetLength() && found == nullptr; ++i) {
-    mirror::ArtField* f = fields->Get(i);
+  ArtField* found = nullptr;
+  ArtField* fields = klass->GetIFields();
+  for (int32_t i = 0, count = klass->NumInstanceFields(); i < count; ++i) {
+    ArtField* f = &fields[i];
     if (name2->Equals(f->GetName())) {
       found = f;
+      break;
     }
   }
   if (found == nullptr) {
     fields = klass->GetSFields();
-    for (int32_t i = 0; i < fields->GetLength() && found == nullptr; ++i) {
-      mirror::ArtField* f = fields->Get(i);
+    for (int32_t i = 0, count = klass->NumStaticFields(); i < count; ++i) {
+      ArtField* f = &fields[i];
       if (name2->Equals(f->GetName())) {
         found = f;
+        break;
       }
     }
   }