Reapply "Incrementally recompute dominators when inlining."

runtime/vm/flow_graph.cc

Index: runtime/vm/flow_graph.cc
diff --git a/runtime/vm/flow_graph.cc b/runtime/vm/flow_graph.cc
index ec35849642c05b8935b37f2b77c6e03b7413aba2..c68f7208bd75baadca7297d8463c75066698a33d 100644
--- a/runtime/vm/flow_graph.cc
+++ b/runtime/vm/flow_graph.cc
@@ -29,8 +29,7 @@ FlowGraph::FlowGraph(const FlowGraphBuilder& builder,
     graph_entry_(graph_entry),
     preorder_(),
     postorder_(),
-    reverse_postorder_(),
-    invalid_dominator_tree_(true) {
+    reverse_postorder_() {
   DiscoverBlocks();
 }
 
@@ -231,7 +230,6 @@ void FlowGraph::ComputeSSA(intptr_t next_virtual_register_number,
 //     (preorder block numbers of) blocks in the dominance frontier.
 void FlowGraph::ComputeDominators(
     GrowableArray<BitVector*>* dominance_frontier) {
-  invalid_dominator_tree_ = false;
   // Use the SEMI-NCA algorithm to compute dominators.  This is a two-pass
   // version of the Lengauer-Tarjan algorithm (LT is normally three passes)
   // that eliminates a pass by using nearest-common ancestor (NCA) to
@@ -673,15 +671,6 @@ void FlowGraph::Bailout(const char* reason) const {
 }
 
 
-void FlowGraph::RepairGraphAfterInlining() {
-  DiscoverBlocks();
-  if (invalid_dominator_tree_) {
-    GrowableArray<BitVector*> dominance_frontier;
-    ComputeDominators(&dominance_frontier);
-  }
-}
-
-
 intptr_t FlowGraph::InstructionCount() const {
   intptr_t size = 0;
   // Iterate each block, skipping the graph entry.