Revert "Headless: don't run unload hooks upon web contents close."

This reverts commit 0d53513.

Reason for revert: Flaky tests, see bug

Bug: 854143

Original change's description:
> Headless: don't run unload hooks upon web contents close.
> 
> Change-Id: I6e391fadbbf47aa6427a16495bdca3c88d456b05
> Reviewed-on: https://chromium-review.googlesource.com/1105041
> Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
> Commit-Queue: Pavel Feldman <pfeldman@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#568213}

TBR=dgozman@chromium.org,pfeldman@chromium.org,eseckler@chromium.org

Change-Id: I252909f78e6d33b98819f6510f780997327a6901
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/1106077
Reviewed-by: Marc Treib <treib@chromium.org>
Commit-Queue: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568417}

headless/lib/browser/headless_web_contents_impl.cc

@@ -95,7 +95,7 @@ class HeadlessWebContentsImpl::Delegate : public content::WebContentsDelegate {
     auto* const headless_contents =
         HeadlessWebContentsImpl::From(browser(), source);
     DCHECK(headless_contents);
-    headless_contents->Close();
+    headless_contents->DelegateRequestsClose();
   }
 
   void AddNewContents(content::WebContents* source,
@@ -379,9 +379,29 @@ bool HeadlessWebContentsImpl::OpenURL(const GURL& url) {
 
 void HeadlessWebContentsImpl::Close() {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
+  if (quit_closure_)
+    return;
+
+  if (!render_process_exited_) {
+    web_contents_->ClosePage();
+    base::RunLoop run_loop(base::RunLoop::Type::kNestableTasksAllowed);
+    quit_closure_ = run_loop.QuitClosure();
+    run_loop.Run();
+  }
+
   browser_context()->DestroyWebContents(this);
 }
 
+void HeadlessWebContentsImpl::DelegateRequestsClose() {
+  if (quit_closure_) {
+    quit_closure_.Run();
+    quit_closure_ = base::Closure();
+  } else {
+    browser_context()->DestroyWebContents(this);
+  }
+}
+
 std::string HeadlessWebContentsImpl::GetDevToolsAgentHostId() {
   return agent_host_->GetId();
 }

headless/lib/browser/headless_web_contents_impl.h

@@ -99,6 +99,8 @@ class HEADLESS_EXPORT HeadlessWebContentsImpl
 
   void Close() override;
 
+  void DelegateRequestsClose();
+
   std::string GetDevToolsAgentHostId();
 
   HeadlessBrowserImpl* browser() const;
@@ -176,6 +178,8 @@ class HEADLESS_EXPORT HeadlessWebContentsImpl
 
   base::ObserverList<HeadlessWebContents::Observer> observers_;
 
+  base::Closure quit_closure_;
+
   base::WeakPtrFactory<HeadlessWebContentsImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(HeadlessWebContentsImpl);