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/oat_file_assistant_test.cc b/runtime/oat_file_assistant_test.cc
index d2362a2..37c6353 100644
--- a/runtime/oat_file_assistant_test.cc
+++ b/runtime/oat_file_assistant_test.cc
@@ -25,11 +25,11 @@
 #include <backtrace/BacktraceMap.h>
 #include <gtest/gtest.h>
 
+#include "art_field-inl.h"
 #include "class_linker.h"
 #include "common_runtime_test.h"
 #include "compiler_callbacks.h"
 #include "mem_map.h"
-#include "mirror/art_field-inl.h"
 #include "os.h"
 #include "scoped_thread_state_change.h"
 #include "thread-inl.h"
@@ -959,25 +959,25 @@
   ASSERT_FALSE(dexfile.Get() == nullptr);
   linker->EnsureInitialized(soa.Self(), dexfile, true, true);
 
-  mirror::ArtField* no_dexopt_needed = mirror::Class::FindStaticField(
+  ArtField* no_dexopt_needed = mirror::Class::FindStaticField(
       soa.Self(), dexfile, "NO_DEXOPT_NEEDED", "I");
   ASSERT_FALSE(no_dexopt_needed == nullptr);
   EXPECT_EQ(no_dexopt_needed->GetTypeAsPrimitiveType(), Primitive::kPrimInt);
   EXPECT_EQ(OatFileAssistant::kNoDexOptNeeded, no_dexopt_needed->GetInt(dexfile.Get()));
 
-  mirror::ArtField* dex2oat_needed = mirror::Class::FindStaticField(
+  ArtField* dex2oat_needed = mirror::Class::FindStaticField(
       soa.Self(), dexfile, "DEX2OAT_NEEDED", "I");
   ASSERT_FALSE(dex2oat_needed == nullptr);
   EXPECT_EQ(dex2oat_needed->GetTypeAsPrimitiveType(), Primitive::kPrimInt);
   EXPECT_EQ(OatFileAssistant::kDex2OatNeeded, dex2oat_needed->GetInt(dexfile.Get()));
 
-  mirror::ArtField* patchoat_needed = mirror::Class::FindStaticField(
+  ArtField* patchoat_needed = mirror::Class::FindStaticField(
       soa.Self(), dexfile, "PATCHOAT_NEEDED", "I");
   ASSERT_FALSE(patchoat_needed == nullptr);
   EXPECT_EQ(patchoat_needed->GetTypeAsPrimitiveType(), Primitive::kPrimInt);
   EXPECT_EQ(OatFileAssistant::kPatchOatNeeded, patchoat_needed->GetInt(dexfile.Get()));
 
-  mirror::ArtField* self_patchoat_needed = mirror::Class::FindStaticField(
+  ArtField* self_patchoat_needed = mirror::Class::FindStaticField(
       soa.Self(), dexfile, "SELF_PATCHOAT_NEEDED", "I");
   ASSERT_FALSE(self_patchoat_needed == nullptr);
   EXPECT_EQ(self_patchoat_needed->GetTypeAsPrimitiveType(), Primitive::kPrimInt);