Fix an outstanding compaction bug in interpreter.

Fixed a bug in DoFieldPut where the FieldHelper GetType could cause
thread suspension which would result in a stale obj.

Added more handles in the class linker to facilitate moving fiels
and methods in the future.

Removed un-necessarly passing handle references since these are value
types and don't need to be passed by reference.

Added a special NullHandle type which allows null handles without a
handle scope.

Change-Id: I1b51723920a2e4f4f8b2907066f578a3e879fd5b
diff --git a/runtime/mirror/stack_trace_element.cc b/runtime/mirror/stack_trace_element.cc
index d8591cc..b1de2b6 100644
--- a/runtime/mirror/stack_trace_element.cc
+++ b/runtime/mirror/stack_trace_element.cc
@@ -39,10 +39,8 @@
   java_lang_StackTraceElement_ = NULL;
 }
 
-StackTraceElement* StackTraceElement::Alloc(Thread* self,
-                                            Handle<String>& declaring_class,
-                                            Handle<String>& method_name,
-                                            Handle<String>& file_name,
+StackTraceElement* StackTraceElement::Alloc(Thread* self, Handle<String> declaring_class,
+                                            Handle<String> method_name, Handle<String> file_name,
                                             int32_t line_number) {
   StackTraceElement* trace =
       down_cast<StackTraceElement*>(GetStackTraceElement()->AllocObject(self));
@@ -57,8 +55,8 @@
 }
 
 template<bool kTransactionActive>
-void StackTraceElement::Init(Handle<String>& declaring_class, Handle<String>& method_name,
-                             Handle<String>& file_name, int32_t line_number) {
+void StackTraceElement::Init(Handle<String> declaring_class, Handle<String> method_name,
+                             Handle<String> file_name, int32_t line_number) {
   SetFieldObject<kTransactionActive>(OFFSET_OF_OBJECT_MEMBER(StackTraceElement, declaring_class_),
                                      declaring_class.Get());
   SetFieldObject<kTransactionActive>(OFFSET_OF_OBJECT_MEMBER(StackTraceElement, method_name_),