Collect getters in a FunctionSet while resolving.

lib/compiler/implementation/ssa/optimize.dart

Index: lib/compiler/implementation/ssa/optimize.dart
===================================================================
--- lib/compiler/implementation/ssa/optimize.dart	(revision 12169)
+++ lib/compiler/implementation/ssa/optimize.dart	(working copy)
@@ -696,7 +696,7 @@
         const SourceString('length'),
         lengthInterceptor.getLibrary());  // TODO(kasperl): Wrong.
     HInvokeInterceptor length = new HInvokeInterceptor(
-        selector, <HInstruction>[interceptor, receiver]);
+        selector, <HInstruction>[interceptor, receiver], true);
     types[length] = HType.INTEGER;
     node.block.addBefore(node, length);
 
@@ -755,6 +755,9 @@
   bool isDeadCode(HInstruction instruction) {
     return !instruction.hasSideEffects(types)
            && instruction.usedBy.isEmpty()
+           // A dynamic getter that has no side effect can still throw
+           // a NoSuchMethodError or a NullPointerException.
+           && instruction is !HInvokeDynamicGetter
            && instruction is !HCheck
            && instruction is !HTypeGuard
            && !instruction.isControlFlow();