Force inlining on trivial accessors.

Make volatility for GetFieldObject a template parameter.
Move some trivial mirror::String routines to a -inl.h.

Bug: 14285442

Change-Id: Ie23b11d4f18cb15a62c3bbb42837a8aaf6b68f92
diff --git a/runtime/native/dalvik_system_DexFile.cc b/runtime/native/dalvik_system_DexFile.cc
index 2231070..953d3a6 100644
--- a/runtime/native/dalvik_system_DexFile.cc
+++ b/runtime/native/dalvik_system_DexFile.cc
@@ -158,6 +158,7 @@
   if (dex_file == nullptr) {
     return;
   }
+  ScopedObjectAccess soa(env);
   if (Runtime::Current()->GetClassLinker()->IsDexFileRegistered(*dex_file)) {
     return;
   }