Inline String isEmpty, refactor inlining of intrinsics.

runtime/vm/flow_graph_optimizer.h

Index: runtime/vm/flow_graph_optimizer.h
===================================================================
--- runtime/vm/flow_graph_optimizer.h	(revision 12881)
+++ runtime/vm/flow_graph_optimizer.h	(working copy)
@@ -64,6 +64,14 @@
 
   bool InstanceCallNeedsClassCheck(InstanceCallInstr* call) const;
 
+  void InlineImplicitInstanceGetter(InstanceCallInstr* call);
+  void InlineArrayLengthGetter(InstanceCallInstr* call,
+                               intptr_t length_offset,
+                               bool is_immutable);
+  void InlineGArrayCapacityGetter(InstanceCallInstr* call);
+  void InlineStringLengthGetter(InstanceCallInstr* call);
+  void InlineStringIsEmptyTester(InstanceCallInstr* call);
+
   FlowGraph* flow_graph_;
 
   DISALLOW_COPY_AND_ASSIGN(FlowGraphOptimizer);