Avoid file IO on UI thread by moving more save-page-as stuff to the FILE thread.

content/browser/download/save_package.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 "content/browser/download/save_package.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 1216 matching lines @@
     // Give backend the lists which contain all resource links that have local
     // storage, after which, render process will serialize DOM for generating
     // HTML data.
     DoSavingProcess();
   } else {
     // No savable frames and/or resources - treat it as user cancel.
     Cancel(true);
   }
 }
 
+// static
 base::FilePath SavePackage::GetSuggestedNameForSaveAs(
+    const base::string16& title,
+    const GURL& page_url,
     bool can_save_as_complete,
     const std::string& contents_mime_type) {
-  DCHECK_CURRENTLY_ON(BrowserThread::UI);
-  base::FilePath name_with_proper_ext = base::FilePath::FromUTF16Unsafe(title_);
+  base::FilePath name_with_proper_ext = base::FilePath::FromUTF16Unsafe(title);
 
   // If the page's title matches its URL, use the URL. Try to use the last path
   // component or if there is none, the domain as the file name.
   // Normally we want to base the filename on the page title, or if it doesn't
   // exist, on the URL. It's not easy to tell if the page has no title, because
   // if the page has no title, WebContents::GetTitle() will return the page's
   // URL (adjusted for display purposes). Therefore, we convert the "title"
   // back to a URL, and if it matches the original page URL, we know the page
   // had no title (or had a title equal to its URL, which is fine to treat
   // similarly).
-  if (title_ == url_formatter::FormatUrl(page_url_)) {
+  if (title == url_formatter::FormatUrl(page_url)) {
     std::string url_path;
-    if (!page_url_.SchemeIs(url::kDataScheme)) {
+    if (!page_url.SchemeIs(url::kDataScheme)) {
       std::vector<std::string> url_parts = base::SplitString(
-          page_url_.path(), "/", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
+          page_url.path(), "/", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
       if (!url_parts.empty()) {
         for (int i = static_cast<int>(url_parts.size()) - 1; i >= 0; --i) {
           url_path = url_parts[i];
           if (!url_path.empty())
             break;
         }
       }
       if (url_path.empty())
-        url_path = page_url_.host();
+        url_path = page_url.host();
     } else {
       url_path = "dataurl";
     }
     name_with_proper_ext = base::FilePath::FromUTF8Unsafe(url_path);
   }
 
   // Ask user for getting final saving name.
   name_with_proper_ext = EnsureMimeExtension(name_with_proper_ext,
                                              contents_mime_type);
   // Adjust extension for complete types.
@@ skipping 66 matching lines @@
   base::FilePath download_save_dir;
   bool skip_dir_check = false;
   auto* delegate = download_manager_->GetDelegate();
   if (delegate) {
     delegate->GetSaveDir(
         web_contents()->GetBrowserContext(), &website_save_dir,
         &download_save_dir, &skip_dir_check);
   }
   std::string mime_type = web_contents()->GetContentsMimeType();
   bool can_save_as_complete = CanSaveAsComplete(mime_type);
-  base::FilePath suggested_filename =
-      GetSuggestedNameForSaveAs(can_save_as_complete, mime_type);
   BrowserThread::PostTaskAndReplyWithResult(
       BrowserThread::FILE, FROM_HERE,
-      base::Bind(&SavePackage::CreateDirectoryOnFileThread, website_save_dir,
-                 download_save_dir, suggested_filename, skip_dir_check),
+      base::Bind(&SavePackage::CreateDirectoryOnFileThread, title_, page_url_,
+                 can_save_as_complete, mime_type, website_save_dir,
+                 download_save_dir, skip_dir_check),
       base::Bind(&SavePackage::ContinueGetSaveInfo, this,
                  can_save_as_complete));
 }
 
 // static
 base::FilePath SavePackage::CreateDirectoryOnFileThread(
+    const base::string16& title,
+    const GURL& page_url,
+    bool can_save_as_complete,
+    const std::string& mime_type,
     const base::FilePath& website_save_dir,
     const base::FilePath& download_save_dir,
-    const base::FilePath& suggested_filename,
     bool skip_dir_check) {
   DCHECK_CURRENTLY_ON(BrowserThread::FILE);
 
+  base::FilePath suggested_filename = GetSuggestedNameForSaveAs(
+      title, page_url, can_save_as_complete, mime_type);
+
   base::FilePath save_dir;
   // If the default html/websites save folder doesn't exist...
   // We skip the directory check for gdata directories on ChromeOS.
   if (!skip_dir_check && !base::DirectoryExists(website_save_dir)) {
     // If the default download dir doesn't exist, create it.
     if (!base::DirectoryExists(download_save_dir)) {
       bool res = base::CreateDirectory(download_save_dir);
       DCHECK(res);
     }
     save_dir = download_save_dir;
@@ skipping 84 matching lines @@
 }
 
 void SavePackage::FinalizeDownloadEntry() {
   DCHECK(download_);
 
   download_manager_->OnSavePackageSuccessfullyFinished(download_);
   RemoveObservers();
 }
 
 }  // namespace content