Add pass to remove empty blocks and recompute fall-through targets.

runtime/vm/flow_graph_compiler_arm.cc

Index: runtime/vm/flow_graph_compiler_arm.cc
diff --git a/runtime/vm/flow_graph_compiler_arm.cc b/runtime/vm/flow_graph_compiler_arm.cc
index 83edec55f738b25295a264f1d405d359e4b4509a..e233a840a636248868549d32debcb2ac0706faae 100644
--- a/runtime/vm/flow_graph_compiler_arm.cc
+++ b/runtime/vm/flow_graph_compiler_arm.cc
@@ -29,7 +29,7 @@ FlowGraphCompiler::~FlowGraphCompiler() {
   // BlockInfos are zone-allocated, so their destructors are not called.
   // Verify the labels explicitly here.
   for (int i = 0; i < block_info_.length(); ++i) {
-    ASSERT(!block_info_[i]->label.IsLinked());
+    ASSERT(!block_info_[i]->jump_label()->IsLinked());
   }
 }