[M131] Fix an issue that a null callback is passed when hitting

back/forward button on PDF

the callback is moved, so changing the code order to avoid using a null cb

(cherry picked from commit 6567bbee)

Low-Coverage-Reason: TRIVIAL_CHANGE
Bug: 377301543
Change-Id: I296466d6873e7f2edf9746717585273670e0ce5f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5988331


Reviewed-by: Shu Yang <shuyng@google.com>
Commit-Queue: Min Qin <qinmin@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1377757}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5989723


Reviewed-by: Min Qin <qinmin@chromium.org>
Commit-Queue: Shu Yang <shuyng@google.com>
Cr-Commit-Position: refs/branch-heads/6778@{#1725}
Cr-Branched-From: b21671ca-refs/heads/main@{#1368529}

chrome/browser/download/chrome_download_manager_delegate.cc

@@ -2021,9 +2021,6 @@ void ChromeDownloadManagerDelegate::CheckDownloadAllowed(
     return;
   }
 
-  CanDownloadCallback cb = base::BindOnce(
-      &ChromeDownloadManagerDelegate::OnCheckDownloadAllowedComplete,
-      weak_ptr_factory_.GetWeakPtr(), std::move(check_download_allowed_cb));
 #if BUILDFLAG(IS_ANDROID)
   if (ShouldOpenPdfInline() && mime_type == pdf::kPDFMimeType) {
     // If this is a forward/back navigation, the native page should trigger a
@@ -2036,6 +2033,13 @@ void ChromeDownloadManagerDelegate::CheckDownloadAllowed(
     }
     NewNavigationObserver::GetInstance()->StartObserving(web_contents);
   }
+#endif
+
+  CanDownloadCallback cb = base::BindOnce(
+      &ChromeDownloadManagerDelegate::OnCheckDownloadAllowedComplete,
+      weak_ptr_factory_.GetWeakPtr(), std::move(check_download_allowed_cb));
+
+#if BUILDFLAG(IS_ANDROID)
   DownloadControllerBase::Get()->AcquireFileAccessPermission(
       web_contents_getter,
       base::BindOnce(&OnDownloadAcquireFileAccessPermissionDone,