Fixes for checked mode and change buildbot script to run dart2js tests in checked mode also.

lib/compiler/implementation/ssa/nodes.dart

Index: lib/compiler/implementation/ssa/nodes.dart
===================================================================
--- lib/compiler/implementation/ssa/nodes.dart	(revision 8378)
+++ lib/compiler/implementation/ssa/nodes.dart	(working copy)
@@ -964,16 +964,27 @@
   bool dataEquals(HInstruction other) => true;
 }
 
-class HCheck extends HInstruction {
+/**
+ * A [HCheck] instruction is an instruction that might do a dynamic
+ * check at runtime on another instruction. To have proper instruction
+ * dependencies in the graph, instructions that depend on the check
+ * being done reference the [HCheck] instruction instead of the
+ * instruction itself.
+ */
+abstract class HCheck extends HInstruction {
   HCheck(inputs) : super(inputs);
-
-  // TODO(floitsch): make class abstract instead of adding an abstract method.
-  abstract accept(HVisitor visitor);
-
   HInstruction get checkedInput() => inputs[0];
 }
 
-class HTypeGuard extends HCheck {
+/**
+ * A [HCheckStatement] instruction is a [HCheck instruction] that
+ * cannot be generated as an expression.
+ */
+abstract class HCheckStatement extends HCheck {
+  HCheckStatement(inputs) : super(inputs);
+}
+
+class HTypeGuard extends HCheckStatement {
   final int state;
   final HType guardedType;
   bool isOn = false;
@@ -1001,7 +1012,7 @@
   bool dataEquals(HTypeGuard other) => guardedType == other.guardedType;
 }
 
-class HBoundsCheck extends HCheck {
+class HBoundsCheck extends HCheckStatement {
   static final int ALWAYS_FALSE = 0;
   static final int FULL_CHECK = 1;
   static final int ALWAYS_ABOVE_ZERO = 2;
@@ -1031,7 +1042,7 @@
   bool dataEquals(HInstruction other) => true;
 }
 
-class HIntegerCheck extends HCheck {
+class HIntegerCheck extends HCheckStatement {
   bool alwaysFalse = false;
 
   HIntegerCheck(value) : super(<HInstruction>[value]);