[debugger] basic test infrastructure for new debugger test api.

src/d8.h

Index: src/d8.h
diff --git a/src/d8.h b/src/d8.h
index e831f8eabf69f2db5e7ea4e9e925202867eaf2f5..16de77d570f682c6824af2f9fb94d9dfa735716f 100644
--- a/src/d8.h
+++ b/src/d8.h
@@ -274,6 +274,7 @@ class ShellOptions {
         dump_heap_constants(false),
         expected_to_throw(false),
         mock_arraybuffer_allocator(false),
+        enable_inspector(false),
         num_isolates(1),
         compile_options(v8::ScriptCompiler::kNoCompileOptions),
         isolate_sources(NULL),
@@ -303,6 +304,7 @@ class ShellOptions {
   bool dump_heap_constants;
   bool expected_to_throw;
   bool mock_arraybuffer_allocator;
+  bool enable_inspector;
   int num_isolates;
   v8::ScriptCompiler::CompileOptions compile_options;
   SourceGroup* isolate_sources;