Revert "Revert "Store resolved Strings for AOT code in .bss.""

Fixed oat_test to keep dex files alive. Fixed mips build.
Rewritten the .bss GC root visiting and added write barrier
to the artResolveStringFromCode().

Test: build aosp_mips-eng
Test: m ART_DEFAULT_GC_TYPE=SS test-art-target-host-gtest-oat_test
Test: Run ART test suite on host and Nexus 9.
Bug: 20323084
Bug: 30627598

This reverts commit 5f926055cb88089d8ca27243f35a9dfd89d981f0.

Change-Id: I07fa2278d82b8eb64964c9a4b66cb93726ccda6b
diff --git a/compiler/optimizing/pc_relative_fixups_x86.cc b/compiler/optimizing/pc_relative_fixups_x86.cc
index 75587af..b1fdb17 100644
--- a/compiler/optimizing/pc_relative_fixups_x86.cc
+++ b/compiler/optimizing/pc_relative_fixups_x86.cc
@@ -92,7 +92,7 @@
   void VisitLoadString(HLoadString* load_string) OVERRIDE {
     HLoadString::LoadKind load_kind = load_string->GetLoadKind();
     if (load_kind == HLoadString::LoadKind::kBootImageLinkTimePcRelative ||
-        load_kind == HLoadString::LoadKind::kDexCachePcRelative) {
+        load_kind == HLoadString::LoadKind::kBssEntry) {
       InitializePCRelativeBasePointer();
       load_string->AddSpecialInput(base_);
     }