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/mirror/dex_cache_test.cc b/runtime/mirror/dex_cache_test.cc
index 53e5534..1d6846b 100644
--- a/runtime/mirror/dex_cache_test.cc
+++ b/runtime/mirror/dex_cache_test.cc
@@ -47,7 +47,7 @@
   EXPECT_LE(0, dex_cache->GetStrings()->GetLength());
   EXPECT_LE(0, dex_cache->GetResolvedTypes()->GetLength());
   EXPECT_LE(0, dex_cache->GetResolvedMethods()->GetLength());
-  EXPECT_LE(0, dex_cache->GetResolvedFields()->GetLength());
+  EXPECT_LE(0u, dex_cache->NumResolvedFields());
 
   EXPECT_EQ(java_lang_dex_file_->NumStringIds(),
             static_cast<uint32_t>(dex_cache->GetStrings()->GetLength()));
@@ -55,8 +55,7 @@
             static_cast<uint32_t>(dex_cache->GetResolvedTypes()->GetLength()));
   EXPECT_EQ(java_lang_dex_file_->NumMethodIds(),
             static_cast<uint32_t>(dex_cache->GetResolvedMethods()->GetLength()));
-  EXPECT_EQ(java_lang_dex_file_->NumFieldIds(),
-            static_cast<uint32_t>(dex_cache->GetResolvedFields()->GetLength()));
+  EXPECT_EQ(java_lang_dex_file_->NumFieldIds(), dex_cache->NumResolvedFields());
 }
 
 }  // namespace mirror