move file access permission logic to DownloadResourceThrottle

chrome/browser/download/download_resource_throttle.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/download/download_resource_throttle.h"
 
 #include "base/bind.h"
 #include "chrome/browser/download/download_stats.h"
+#include "content/public/browser/browser_thread.h"
 #include "content/public/browser/resource_controller.h"
 
+#if defined(OS_ANDROID)
+#include "content/public/browser/android/download_controller_android.h"
+#include "content/public/browser/render_view_host.h"
+
+using content::DownloadControllerAndroid;
+#endif
+
+using content::BrowserThread;
+
+namespace {
+
+void OnCanDownloadDecided(
+    const DownloadRequestLimiter::Callback& callback, bool allow) {
+  BrowserThread::PostTask(
+      BrowserThread::IO, FROM_HERE, base::Bind(callback, allow));
+}
+
+#if defined(OS_ANDROID)
+void OnAcquireFileAccessPermissionDone(
+    const base::Closure& can_download_callback,
+    const DownloadRequestLimiter::Callback& cancel_callback,
+    bool granted) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  if (granted)
+    can_download_callback.Run();
+  else
+    OnCanDownloadDecided(cancel_callback, false);
+}
+
+void AcquireFileAccessPermission(
+    int render_process_id,
+    int render_view_id,
+    const base::Closure& can_download_callback,
+    const DownloadRequestLimiter::Callback& cancel_callback) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  content::DownloadControllerAndroid::Get()->AcquireFileAccessPermission(
+      render_process_id, render_view_id, base::Bind(
+          &OnAcquireFileAccessPermissionDone,
+          can_download_callback, cancel_callback));
+}
+#endif
+
+}  // namespace
+
 DownloadResourceThrottle::DownloadResourceThrottle(
-    DownloadRequestLimiter* limiter,
+    scoped_refptr<DownloadRequestLimiter> limiter,
     int render_process_id,
     int render_view_id,
     const GURL& url,
     const std::string& request_method)
     : querying_limiter_(true),
       request_allowed_(false),
       request_deferred_(false) {
-  limiter->CanDownloadOnIOThread(
-      render_process_id,
-      render_view_id,
-      url,
-      request_method,
-      base::Bind(&DownloadResourceThrottle::ContinueDownload,
-                 AsWeakPtr()));
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  DownloadRequestLimiter::Callback continue_callback = base::Bind(

[asanka, 2015/07/20 20:15:24]

Given that none of this logic needs to happen on the IO thread (save for the
AsWeakPtr() call, which can still be done here), how about moving this logic to
a function on the UI thread?

That way we can avoid all the abstract callbacks and have concrete function
calls.

[qinmin, 2015/07/20 22:11:02]

Done. Still leaves DownloadResourceThrottle on the IO thread, and refactored the
static functions on the UI thread

+      &DownloadResourceThrottle::ContinueDownload, AsWeakPtr());
+  base::Closure can_download_callback = base::Bind(
+      &DownloadRequestLimiter::CanDownload, limiter, render_process_id,
+      render_view_id, url, request_method, base::Bind(
+          &OnCanDownloadDecided, continue_callback));
+#if defined(OS_ANDROID)
+  BrowserThread::PostTask(
+      BrowserThread::UI, FROM_HERE, base::Bind(
+          &AcquireFileAccessPermission, render_process_id, render_view_id,
+          can_download_callback, continue_callback));
+#else
+  BrowserThread::PostTask(BrowserThread::UI, FROM_HERE, can_download_callback);
+#endif
 }
 
 DownloadResourceThrottle::~DownloadResourceThrottle() {
 }
 
 void DownloadResourceThrottle::WillStartRequest(bool* defer) {
   WillDownload(defer);
 }
 
 void DownloadResourceThrottle::WillRedirectRequest(
@@ skipping 18 matching lines @@
     request_deferred_ = true;
     *defer = true;
     return;
   }
 
   if (!request_allowed_)
     controller()->Cancel();
 }
 
 void DownloadResourceThrottle::ContinueDownload(bool allow) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
   querying_limiter_ = false;
   request_allowed_ = allow;
 
   if (allow) {
     // Presumes all downloads initiated by navigation use this throttle and
     // nothing else does.
     RecordDownloadSource(DOWNLOAD_INITIATED_BY_NAVIGATION);
   } else {
     RecordDownloadCount(CHROME_DOWNLOAD_COUNT_BLOCKED_BY_THROTTLING);
   }
 
   if (request_deferred_) {
     request_deferred_ = false;
     if (allow) {
       controller()->Resume();
     } else {
       controller()->Cancel();
     }
   }
 }