Revert "Type and constant propagator should guard against mutable class ids."

runtime/vm/flow_graph_type_propagator.cc

Index: runtime/vm/flow_graph_type_propagator.cc
diff --git a/runtime/vm/flow_graph_type_propagator.cc b/runtime/vm/flow_graph_type_propagator.cc
index 0d646b873fe13ff5d5894b33226e08d522901908..2b7001f656104549b25930aefbf2c9124cc4f30f 100644
--- a/runtime/vm/flow_graph_type_propagator.cc
+++ b/runtime/vm/flow_graph_type_propagator.cc
@@ -149,7 +149,7 @@ void FlowGraphTypePropagator::PropagateRecursive(BlockEntryInstr* block) {
     }
   }
 
-  HandleBranchOnStrictCompare(block);
+  HandleBranchOnNull(block);
 
   for (intptr_t i = 0; i < block->dominated_blocks().length(); ++i) {
     PropagateRecursive(block->dominated_blocks()[i]);
@@ -159,8 +159,7 @@ void FlowGraphTypePropagator::PropagateRecursive(BlockEntryInstr* block) {
 }
 
 
-void FlowGraphTypePropagator::HandleBranchOnStrictCompare(
-    BlockEntryInstr* block) {
+void FlowGraphTypePropagator::HandleBranchOnNull(BlockEntryInstr* block) {
   BranchInstr* branch = block->last_instruction()->AsBranch();
   if (branch == NULL) {
     return;
@@ -319,9 +318,7 @@ void FlowGraphTypePropagator::VisitCheckClassId(CheckClassIdInstr* check) {
 void FlowGraphTypePropagator::VisitGuardFieldClass(
     GuardFieldClassInstr* guard) {
   const intptr_t cid = guard->field().guarded_cid();
-  if ((cid == kIllegalCid) ||
-      (cid == kDynamicCid) ||
-      !CheckClassInstr::IsImmutableClassId(cid)) {
+  if ((cid == kIllegalCid) || (cid == kDynamicCid)) {
     return;
   }
 
@@ -797,17 +794,13 @@ CompileType ConstantInstr::ComputeType() const {
     return CompileType::Null();
   }
 
-  intptr_t cid = value().GetClassId();
-  if (!CheckClassInstr::IsImmutableClassId(cid)) {
-    cid = kDynamicCid;
-  }
-
   if (value().IsInstance()) {
-    return CompileType::Create(cid,
+    return CompileType::Create(
+        value().GetClassId(),
         AbstractType::ZoneHandle(Instance::Cast(value()).GetType()));
   } else {
     // Type info for non-instance objects.
-    return CompileType::FromCid(cid);
+    return CompileType::FromCid(value().GetClassId());
   }
 }
 
@@ -981,9 +974,6 @@ CompileType LoadStaticFieldInstr::ComputeType() const {
       cid = obj.GetClassId();
     }
   }
-  if (!CheckClassInstr::IsImmutableClassId(cid)) {
-    cid = kDynamicCid;
-  }
   return CompileType(is_nullable, cid, abstract_type);
 }