Revert "Worker: Implement WorkerGlobalScope::ImportModuleScript()"

This reverts commit 715a1c5f5b3dd2e40219c5457c15e62f4726a503.

Reason for revert:
This causes compile failures on some bots.

Original change's description:
> Worker: Implement WorkerGlobalScope::ImportModuleScript()
> 
> This CL implements WorkerGlobalScope::ImportModuleScript() that imports module
> scripts using WorkerModulatorImpl, and wires up DedicatedWorkerMessagingProxy
> via WorkerThread.
> 
> Note that module workers are still not available because WorkerOptions is not
> exposed on the ctor of Worker and WorkerModulatorImpl is not fully implemented
> yet.
> 
> Design doc: https://docs.google.com/a/chromium.org/document/d/1IMGWAK7Wq37mLehwkbysNRBBnhQBo3z2MbYyMkViEnY/edit?usp=sharing
> 
> Bug: 680046
> Change-Id: I0c616b7a1b79abb02c1085be356293510dd4c04b
> Reviewed-on: https://chromium-review.googlesource.com/807675
> Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
> Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
> Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#525270}

TBR=kinuko@chromium.org,kouhei@chromium.org,nhiroki@chromium.org

Change-Id: I253df9d13bbb8bc63cae7bb018fd10c4ee311d25
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 680046
Reviewed-on: https://chromium-review.googlesource.com/836187
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
Cr-Commit-Position: refs/heads/master@{#525273}
8 files changed