Reapply "Incrementally recompute dominators when inlining."

runtime/vm/flow_graph.h

Index: runtime/vm/flow_graph.h
diff --git a/runtime/vm/flow_graph.h b/runtime/vm/flow_graph.h
index 022f21fee9eeb31f5c42ce659de9c3db3cf1766f..1bb43668fe22d1d8672948e48bb20bcac022f076 100644
--- a/runtime/vm/flow_graph.h
+++ b/runtime/vm/flow_graph.h
@@ -129,25 +129,21 @@ class FlowGraph : public ZoneAllocated {
   // body blocks for each loop header.
   void ComputeLoops(GrowableArray<BlockEntryInstr*>* loop_headers);
 
-  void RepairGraphAfterInlining();
-
   // TODO(zerny): Once the SSA is feature complete this should be removed.
   void Bailout(const char* reason) const;
 
-  void InvalidateDominatorTree() { invalid_dominator_tree_ = true; }
-
 #ifdef DEBUG
   // Verification methods for debugging.
   bool VerifyUseLists();
 #endif  // DEBUG
 
+  void DiscoverBlocks();
+
  private:
   friend class IfConverter;
   friend class BranchSimplifier;
   friend class ConstantPropagator;
 
-  void DiscoverBlocks();
-
   // SSA transformation methods and fields.
   void ComputeDominators(GrowableArray<BitVector*>* dominance_frontier);
 
@@ -191,7 +187,6 @@ class FlowGraph : public ZoneAllocated {
   GrowableArray<BlockEntryInstr*> preorder_;
   GrowableArray<BlockEntryInstr*> postorder_;
   GrowableArray<BlockEntryInstr*> reverse_postorder_;
-  bool invalid_dominator_tree_;
   ConstantInstr* constant_null_;
 };