Set statically known ResultCid for AllocateObject.

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 93b89ffc76daf82942794b275c64755e8ffead03..1933f8d7565e002cb8a576e7f0faba9188ce0014 100644
--- a/runtime/vm/intermediate_language.cc
+++ b/runtime/vm/intermediate_language.cc
@@ -1748,12 +1748,19 @@ Definition* StrictCompareInstr::Canonicalize(FlowGraphOptimizer* optimizer) {
 
 Instruction* CheckClassInstr::Canonicalize(FlowGraphOptimizer* optimizer) {
   const intptr_t value_cid = value()->ResultCid();
+  if (value_cid == kDynamicCid) {
+    return this;
+  }
+
   const intptr_t num_checks = unary_checks().NumberOfChecks();
-  if ((num_checks == 1) &&
-      (value_cid == unary_checks().GetReceiverClassIdAt(0))) {
-    // No checks needed.
-    return NULL;
+
+  for (intptr_t i = 0; i < num_checks; i++) {
+    if (value_cid == unary_checks().GetReceiverClassIdAt(i)) {
+      // No checks needed.
+      return NULL;
+    }
   }
+
   return this;
 }