More work for background compilation; move pending_functions_ from ObjectStore to Thread.

runtime/vm/isolate.cc

Index: runtime/vm/isolate.cc
diff --git a/runtime/vm/isolate.cc b/runtime/vm/isolate.cc
index 33048344a5e8c83ce2d408c8f812f2d10bf6e5ec..5e4b46ad665770e812a7d1d5779aa8b7ca44da2d 100644
--- a/runtime/vm/isolate.cc
+++ b/runtime/vm/isolate.cc
@@ -736,7 +736,6 @@ Isolate::Isolate(const Dart_IsolateFlags& api_flags)
   :   stack_limit_(0),
       store_buffer_(new StoreBuffer()),
       heap_(NULL),
-      vm_tag_(0),
       user_tag_(0),
       current_tag_(UserTag::null()),
       default_tag_(UserTag::null()),
@@ -777,7 +776,6 @@ Isolate::Isolate(const Dart_IsolateFlags& api_flags)
       gc_epilogue_callback_(NULL),
       defer_finalization_count_(0),
       deopt_context_(NULL),
-      background_compiler_(NULL),
       compiler_stats_(NULL),
       is_service_isolate_(false),
       stacktrace_(NULL),
@@ -789,6 +787,7 @@ Isolate::Isolate(const Dart_IsolateFlags& api_flags)
       profiler_data_(NULL),
       tag_table_(GrowableObjectArray::null()),
       deoptimized_code_array_(GrowableObjectArray::null()),
+      background_compiler_(NULL),
       background_compilation_queue_(GrowableObjectArray::null()),
       pending_service_extension_calls_(GrowableObjectArray::null()),
       registered_service_extension_handlers_(GrowableObjectArray::null()),