dart2js: Inhibit code motion of indexing

pkg/compiler/lib/src/ssa/nodes.dart

Index: pkg/compiler/lib/src/ssa/nodes.dart
diff --git a/pkg/compiler/lib/src/ssa/nodes.dart b/pkg/compiler/lib/src/ssa/nodes.dart
index 3fec3f87be2f26e1ffa7cae80cb3b2350ae00415..a0aafb00ce276783a0884fae91d7ed057fe20b73 100644
--- a/pkg/compiler/lib/src/ssa/nodes.dart
+++ b/pkg/compiler/lib/src/ssa/nodes.dart
@@ -2623,6 +2623,10 @@ class HIndex extends HInstruction {
   HInstruction get receiver => inputs[0];
   HInstruction get index => inputs[1];
 
+  // Implicit dependency on HBoundsCheck or constraints on index.
+  // TODO(27272): Make HIndex dependent on bounds checking.
+  bool get isMovable => false;
+
   HInstruction getDartReceiver(Compiler compiler) => receiver;
   bool onlyThrowsNSM() => true;
   bool canThrow() => receiver.canBeNull();
@@ -2653,6 +2657,10 @@ class HIndexAssign extends HInstruction {
   HInstruction get index => inputs[1];
   HInstruction get value => inputs[2];
 
+  // Implicit dependency on HBoundsCheck or constraints on index.
+  // TODO(27272): Make HIndex dependent on bounds checking.
+  bool get isMovable => false;
+
   HInstruction getDartReceiver(Compiler compiler) => receiver;
   bool onlyThrowsNSM() => true;
   bool canThrow() => receiver.canBeNull();