VM(RegExp): Allow OSR optimization of RegExp :matcher functions.

runtime/vm/intermediate_language.cc

Index: runtime/vm/intermediate_language.cc
diff --git a/runtime/vm/intermediate_language.cc b/runtime/vm/intermediate_language.cc
index cfb7622d3a7f58b48206093d101e2b65f94acd93..fee69357b60a47973a05afb837908085c656d519 100644
--- a/runtime/vm/intermediate_language.cc
+++ b/runtime/vm/intermediate_language.cc
@@ -2066,6 +2066,17 @@ Definition* RedefinitionInstr::Canonicalize(FlowGraph* flow_graph) {
 }
 
 
+Instruction* CheckStackOverflowInstr::Canonicalize(FlowGraph* flow_graph) {
+  switch (kind_) {
+    case kFull:
+      return this;
+    case kOsrEntry:
+      // Don't need OSR entries in the optimized code.
+      return NULL;
+  }
+}
+
+
 bool LoadFieldInstr::IsImmutableLengthLoad() const {
   switch (recognized_kind()) {
     case MethodRecognizer::kObjectArrayLength: