[interpreter, debugger] implement bytecode break location iterator.

test/unittests/interpreter/bytecode-array-builder-unittest.cc

Index: test/unittests/interpreter/bytecode-array-builder-unittest.cc
diff --git a/test/unittests/interpreter/bytecode-array-builder-unittest.cc b/test/unittests/interpreter/bytecode-array-builder-unittest.cc
index e8ab446e822a88861ebb181a6887d6f36b97a365..ac76a37458ba7e1476345d384e7bd0b49fcf154b 100644
--- a/test/unittests/interpreter/bytecode-array-builder-unittest.cc
+++ b/test/unittests/interpreter/bytecode-array-builder-unittest.cc
@@ -394,7 +394,8 @@ TEST_F(BytecodeArrayBuilderTest, Constants) {
       .LoadLiteral(large_smi)
       .LoadLiteral(heap_num_1)
       .LoadLiteral(heap_num_1)
-      .LoadLiteral(heap_num_2_copy);
+      .LoadLiteral(heap_num_2_copy)
+      .Return();
 
   Handle<BytecodeArray> array = builder.ToBytecodeArray();
   // Should only have one entry for each identical constant.