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 17870)
+++ sdk/lib/_internal/compiler/implementation/ssa/nodes.dart	(working copy)
@@ -1857,6 +1857,23 @@
   bool isDoWhile() {
     return identical(kind, DO_WHILE_LOOP);
   }
+
+  HBasicBlock computeLoopHeader() {
+    HBasicBlock result;
+    if (isDoWhile()) {
+      // In case of a do/while, the successor is a block that avoids
+      // a critical edge and branchs to the loop header.
+      result = block.successors[0].successors[0];
+    } else {
+      // For other loops, the loop header might be up the dominator
+      // tree if the loop condition has control flow.
+      result = block;
+      while (!result.isLoopHeader()) result = result.dominator;
+    }
+
+    assert(result.isLoopHeader());
+    return result;
+  }
 }
 
 class HConstant extends HInstruction {
@@ -2618,6 +2635,8 @@
     return node.accept(const LoopTypeVisitor());
   }
 
+  bool isDoWhile() => kind == DO_WHILE_LOOP;
+
   bool accept(HStatementInformationVisitor visitor) =>
     visitor.visitLoopInfo(this);
 }