[content] Avoid calling DeleteForCurrentDocument from destructor

This CL removes the call to DeleteForCurrentDocument from the destructor
of ManifestManagerHost.

This intends to fix a crash which happens from time to time using
RenderDocumentHostUserData.

Change-Id: I1336fb62328dcb0cf9991499f399bf3665d29b75
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2224737Reviewed-by: Rakina Zata Amni <rakina@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Reviewed-by: Sreeja Kamishetty <sreejakshetty@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Yuzu Saijo <yuzus@chromium.org>
Cr-Commit-Position: refs/heads/master@{#774006}

content/browser/manifest/manifest_manager_host.cc

@@ -22,7 +22,7 @@ ManifestManagerHost::ManifestManagerHost(RenderFrameHost* render_frame_host)
 }
 
 ManifestManagerHost::~ManifestManagerHost() {
-  OnConnectionError();
+  DispatchPendingCallbacks();
 }
 
 void ManifestManagerHost::BindObserver(
@@ -55,7 +55,7 @@ blink::mojom::ManifestManager& ManifestManagerHost::GetManifestManager() {
   return *manifest_manager_;
 }
 
-void ManifestManagerHost::OnConnectionError() {
+void ManifestManagerHost::DispatchPendingCallbacks() {
   std::vector<GetManifestCallback> callbacks;
   for (CallbackMap::iterator it(&callbacks_); !it.IsAtEnd(); it.Advance()) {
     callbacks.push_back(std::move(*it.GetCurrentValue()));
@@ -63,7 +63,10 @@ void ManifestManagerHost::OnConnectionError() {
   callbacks_.Clear();
   for (auto& callback : callbacks)
     std::move(callback).Run(GURL(), blink::Manifest());
+}
 
+void ManifestManagerHost::OnConnectionError() {
+  DispatchPendingCallbacks();
   if (GetForCurrentDocument(manifest_manager_frame_)) {
     DeleteForCurrentDocument(manifest_manager_frame_);
   }

content/browser/manifest/manifest_manager_host.h

@@ -55,6 +55,8 @@ class ManifestManagerHost
   using CallbackMap = base::IDMap<std::unique_ptr<GetManifestCallback>>;
 
   blink::mojom::ManifestManager& GetManifestManager();
+
+  void DispatchPendingCallbacks();
   void OnConnectionError();
 
   void OnRequestManifestResponse(int request_id,