Introduce a lazy-compile stub for functions.

runtime/vm/object.cc

Index: runtime/vm/object.cc
===================================================================
--- runtime/vm/object.cc	(revision 34118)
+++ runtime/vm/object.cc	(working copy)
@@ -683,7 +683,7 @@
     PcDescriptors::initializeHandle(
         empty_descriptors_,
         reinterpret_cast<RawPcDescriptors*>(address + kHeapObjectTag));
-    empty_descriptors_->raw_ptr()->length_ = Smi::New(0);
+    empty_descriptors_->raw_ptr()->length_ = 0;
   }
 
 
@@ -4601,16 +4601,29 @@
 }
 
 
-void Function::SetCode(const Code& value) const {
+void Function::set_code(const Code& value) const {
   StorePointer(&raw_ptr()->code_, value.raw());
+}
+
+void Function::AttachCode(const Code& value) const {
+  set_code(value);
   ASSERT(Function::Handle(value.function()).IsNull() ||
     (value.function() == this->raw()));
   value.set_owner(*this);
 }
 
 
+bool Function::HasCode() const {
+  return raw_ptr()->code_ != Code::null()
+      && raw_ptr()->code_ != StubCode::LazyCompileClosure_entry()->code();
+}
+
+
 void Function::ClearCode() const {
-  StorePointer(&raw_ptr()->code_, Code::null());
+  StorePointer(&raw_ptr()->code_,
+               IsClosureFunction()
+               ? StubCode::LazyCompileClosure_entry()->code()
+               : Code::null());
   StorePointer(&raw_ptr()->unoptimized_code_, Code::null());
 }
 
@@ -4637,7 +4650,7 @@
   // Patch entry of the optimized code.
   CodePatcher::PatchEntry(current_code);
   // Use previously compiled unoptimized code.
-  SetCode(Code::Handle(unoptimized_code()));
+  AttachCode(Code::Handle(unoptimized_code()));
   CodePatcher::RestoreEntry(Code::Handle(unoptimized_code()));
 }
 
@@ -5679,6 +5692,8 @@
                     parent_owner,
                     token_pos));
   result.set_parent_function(parent);
+  result.set_code(Code::Handle(StubCode::LazyCompileClosure_entry()->code()));
+
   return result.raw();
 }
 
@@ -9364,14 +9379,12 @@
 
 
 intptr_t PcDescriptors::Length() const {
-  return Smi::Value(raw_ptr()->length_);
+  return raw_ptr()->length_;
 }
 
 
 void PcDescriptors::SetLength(intptr_t value) const {
-  // This is only safe because we create a new Smi, which does not cause
-  // heap allocation.
-  raw_ptr()->length_ = Smi::New(value);
+  raw_ptr()->length_ = value;
 }
 
 
@@ -9573,11 +9586,6 @@
 }
 
 
-void Stackmap::SetCode(const dart::Code& code) const {
-  StorePointer(&raw_ptr()->code_, code.raw());
-}
-
-
 bool Stackmap::GetBit(intptr_t bit_index) const {
   ASSERT(InRange(bit_index));
   int byte_index = bit_index >> kBitsPerByteLog2;