Update WebStore API to disable extensions for ephemeral Guest profiles.

Extensions will be disabled in the first experiments of ephemeral Guest
profiles. WebStore private APIs are updated to treat ephemeral Guest
profiles similar to the off the record ones.

Please see go/ephemeral-guest-profiles for more context.

Bug: 1125474
Change-Id: If4b4711d133f8e429b2ced09fdf6747cb0c31491
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2580805Reviewed-by: David Bertoni <dbertoni@chromium.org>
Commit-Queue: Ramin Halavati <rhalavati@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836030}

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

@@ -784,7 +784,10 @@ WebstorePrivateCompleteInstallFunction::Run() {
   std::unique_ptr<CompleteInstall::Params> params(
       CompleteInstall::Params::Create(*args_));
   EXTENSION_FUNCTION_VALIDATE(params);
+  // TODO(https://crbug.com/1125475): Enable Extensions for Ephemeral Guest
+  // profiles.
   if (chrome_details_.GetProfile()->IsGuestSession() ||
+      chrome_details_.GetProfile()->IsEphemeralGuestProfile() ||
       chrome_details_.GetProfile()->IsOffTheRecord()) {
     return RespondNow(Error(kIncognitoError));
   }
@@ -953,8 +956,11 @@ WebstorePrivateIsInIncognitoModeFunction::
 ExtensionFunction::ResponseAction
 WebstorePrivateIsInIncognitoModeFunction::Run() {
   Profile* profile = chrome_details_.GetProfile();
+  // TODO(https://crbug.com/1125475): Enable Extensions for Ephemeral Guest
+  // profiles.
   return RespondNow(ArgumentList(IsInIncognitoMode::Results::Create(
-      profile != profile->GetOriginalProfile())));
+      profile != profile->GetOriginalProfile() ||
+      profile->IsEphemeralGuestProfile())));
 }
 
 WebstorePrivateLaunchEphemeralAppFunction::