Move a RegisterModuleScript() call to ModuleScript::CreateInternal()

To align with the spec, and also this is needed for inline module
scripts because NotifyNewSingleModuleFinished() is not called for
inline scripts.

This CL also makes DummyModulator to ignore RegisterModuleScript()
calls where it is not tested explcitly, because this CL makes
an additional RegisterModuleScript() call for CreateForTest() which is
not coupled with NotifyNewSingleModuleFinished().

This CL doesn't change the non-test behavior, because in the non-test
code ModuleScript::Create() is always coupled with
NotifyNewSingleModuleFinished() and thus this CL just makes
RegisterModuleScript() a little earlier.

BUG=594639, 715369

Review-Url: https://codereview.chromium.org/2850673002
Cr-Commit-Position: refs/heads/master@{#467907}
4 files changed