[debugger] simplify fetching scripts for inspector.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index ad41d819b7f094ddda7834f5ca57377ae8184f03..e8aa8f188d2d50973b622d9b91cab83fe870f3fc 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -8947,12 +8947,17 @@ void DebugInterface::GetLoadedScripts(
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(v8_isolate);
   ENTER_V8(isolate);
   i::HandleScope handle_scope(isolate);
-  i::Handle<i::FixedArray> instances = isolate->debug()->GetLoadedScripts();
-  for (int i = 0; i < instances->length(); i++) {
-    i::Handle<i::Script> script =
-        i::Handle<i::Script>(i::Script::cast(instances->get(i)));
-    if (script->type() != i::Script::TYPE_NORMAL) continue;
-    scripts.Append(ToApiHandle<Script>(script));
+  i::Factory* factory = isolate->factory();
+  if (!factory->script_list()->IsWeakFixedArray()) return;
+  i::Handle<i::WeakFixedArray> array =
+      i::Handle<i::WeakFixedArray>::cast(factory->script_list());
+  {
+    i::Script::Iterator iterator(isolate);
+    i::Handle<i::Script> script;
+    while (!(script = i::Handle<i::Script>(iterator.Next())).is_null()) {

[kozy, 2016/10/31 14:59:11]

I think that i::Handle<i::Script>(Object*) tries to get isolate from passed
Object [1] and it will produce a crash. And will it work correctly if we pass
isolate as second argument to avoid mentioned crash? It looks for me that
is_null() check returns true only if handle was created with cstor without
arguments, otherwise it just allocates one more handle in handle scope, event if
it's null.

And I've question about how V8 works. Can we just not create a handle and
iterate through raw pointers?
i::Script* script = nullptr;
while ((script = iterator.Next()) != nullptr) {
...
if (script->HasValidSource())
scripts.Append(ToApiHandle<Script>(i::handle(script)));
}
It looks for me like nothing in loop code can call gc to move objects in memory.
What functions call are potentially can run gc?

[1] https://cs.chromium.org/chromium/src/v8/src/handles.h?rcl=1477898213&l=99

[Yang, 2016/11/02 12:25:55]

Good point. I changed the code after running tests. But we at least need the
handle to pass to ToApiHandle.

+      if (script->type() != i::Script::TYPE_NORMAL) continue;
+      if (script->HasValidSource()) scripts.Append(ToApiHandle<Script>(script));
+    }
   }
 }