Reland "Fix issue that webstore private APIs return array improperly"

This reverts commit 350e9c41.

Reason for revert: This CL is not related to AutotestPrivateApiTest.AutotestPrivate failure. The test was flaky before the original CL landed.

Original change's description:
> Revert "Fix issue that webstore private APIs return array improperly"
>
> This reverts commit 0403341d.
>
> Reason for revert: AutotestPrivateApiTest.AutotestPrivate is failing
>
> https://ci.chromium.org/p/chromium/builders/ci/linux-chromeos-dbg/19325
>
> Apologies to developer if reverted in error.
>
> Original change's description:
> > Fix issue that webstore private APIs return array improperly
> >
> > webstorePrivate.getExtensionStatus and requestExtension should return
> > extension status as a string but not an array of string.
> >
> > Bug: 1099334
> > Change-Id: Ib56e466cc1d967e3a322494076ad7640a6868aac
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2267719
> > Commit-Queue: Owen Min <zmin@chromium.org>
> > Reviewed-by: Karan Bhatia <karandeepb@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#782607}
>
> TBR=zmin@chromium.org,karandeepb@chromium.org
>
> Change-Id: Ibe7b886da11ee5864d3b8a73b8ed7d98f53327d6
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: 1099334
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2268839
> Reviewed-by: Chris Mumford <cmumford@google.com>
> Commit-Queue: Chris Mumford <cmumford@google.com>
> Cr-Commit-Position: refs/heads/master@{#782740}

TBR=cmumford@google.com,zmin@chromium.org,karandeepb@chromium.org

# Not skipping CQ checks because this is a reland.

Bug: 1099334
Change-Id: I60e43ed8b5d5450e7143683c2ff1516c5d93f8be
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2268542Reviewed-by: Owen Min <zmin@chromium.org>
Reviewed-by: Karan Bhatia <karandeepb@chromium.org>
Commit-Queue: Owen Min <zmin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#782799}

chrome/browser/extensions/api/webstore_private/webstore_private_api.cc

@@ -1121,7 +1121,7 @@ WebstorePrivateGetExtensionStatusFunction::BuildResponseWithoutManifest(
       GetWebstoreExtensionInstallStatus(extension_id, profile);
   api::webstore_private::ExtensionInstallStatus api_status =
       ConvertExtensionInstallStatusForAPI(status);
-  return OneArgument(GetExtensionStatus::Results::Create(api_status));
+  return ArgumentList(GetExtensionStatus::Results::Create(api_status));
 }
 
 void WebstorePrivateGetExtensionStatusFunction::OnManifestParsed(
@@ -1153,7 +1153,7 @@ void WebstorePrivateGetExtensionStatusFunction::OnManifestParsed(
       PermissionsParser::GetRequiredPermissions(dummy_extension.get()));
   api::webstore_private::ExtensionInstallStatus api_status =
       ConvertExtensionInstallStatusForAPI(status);
-  Respond(OneArgument(GetExtensionStatus::Results::Create(api_status)));
+  Respond(ArgumentList(GetExtensionStatus::Results::Create(api_status)));
 }
 
 WebstorePrivateRequestExtensionFunction::
@@ -1178,7 +1178,8 @@ WebstorePrivateRequestExtensionFunction::Run() {
 
   api::webstore_private::ExtensionInstallStatus api_status =
       ConvertExtensionInstallStatusForAPI(status);
-  return RespondNow(OneArgument(RequestExtension::Results::Create(api_status)));
+  return RespondNow(
+      ArgumentList(RequestExtension::Results::Create(api_status)));
 }
 
 }  // namespace extensions

chrome/browser/extensions/api/webstore_private/webstore_private_unittest.cc

@@ -135,11 +135,8 @@ class WebstorePrivateExtensionInstallRequestBase : public ExtensionApiUnittest {
 
   void VerifyResponse(const ExtensionInstallStatus& expected_response,
                       const base::Value* actual_response) {
-    ASSERT_TRUE(actual_response->is_list());
-    const auto& actual_list = actual_response->GetList();
-    ASSERT_EQ(1u, actual_list.size());
-    ASSERT_TRUE(actual_list[0].is_string());
-    EXPECT_EQ(ToString(expected_response), actual_list[0].GetString());
+    ASSERT_TRUE(actual_response->is_string());
+    EXPECT_EQ(ToString(expected_response), actual_response->GetString());
   }
 
  private: