Fix another bailout problem where not all blocks were visiting when propagating bailout information…

sdk/lib/_internal/compiler/implementation/ssa/nodes.dart

Index: sdk/lib/_internal/compiler/implementation/ssa/nodes.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/ssa/nodes.dart	(revision 17833)
+++ sdk/lib/_internal/compiler/implementation/ssa/nodes.dart	(working copy)
@@ -1857,6 +1857,16 @@
   bool isDoWhile() {
     return identical(kind, DO_WHILE_LOOP);
   }
+
+  HBasicBlock get loopHeader {
+    HBasicBlock result = isDoWhile()
+        // In case of a do/while, the successor is a block that avoids
+        // a critical edge and branchs to the loop header.
+        ? block.successors[0].successors[0]
+        : block;
+    assert(result.isLoopHeader());
+    return result;
+  }
 }
 
 class HConstant extends HInstruction {
@@ -2618,6 +2628,8 @@
     return node.accept(const LoopTypeVisitor());
   }
 
+  bool isDoWhile() => kind == DO_WHILE_LOOP;
+
   bool accept(HStatementInformationVisitor visitor) =>
     visitor.visitLoopInfo(this);
 }