Have net-export's save dialog default to last used save directory

chrome/browser/ui/webui/net_export_ui.cc

 // Copyright (c) 2013 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/ui/webui/net_export_ui.h"
 
 #include <memory>
 #include <string>
 
 #include "base/bind.h"
 #include "base/files/file_util.h"
+#include "base/lazy_instance.h"
 #include "base/macros.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/values.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/platform_util.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/chrome_select_file_policy.h"
 #include "chrome/common/features.h"
 #include "chrome/common/url_constants.h"
@@ skipping 12 matching lines @@
 #if BUILDFLAG(ANDROID_JAVA_UI)
 #include "chrome/browser/android/intent_helper.h"
 #endif
 
 using content::BrowserThread;
 using content::WebContents;
 using content::WebUIMessageHandler;
 
 namespace {
 
+base::LazyInstance<base::FilePath>::Leaky
+    last_save_dir = LAZY_INSTANCE_INITIALIZER;
+
 content::WebUIDataSource* CreateNetExportHTMLSource() {
   content::WebUIDataSource* source =
       content::WebUIDataSource::Create(chrome::kChromeUINetExportHost);
 
   source->SetJsonPath("strings.js");
   source->AddResourcePath(net_log::kNetExportUIJS, IDR_NET_LOG_NET_EXPORT_JS);
   source->SetDefaultResource(IDR_NET_LOG_NET_EXPORT_HTML);
   return source;
 }
 
@@ skipping 133 matching lines @@
                  weak_ptr_factory_.GetWeakPtr(), net_log_file_writer_));
 }
 
 void NetExportMessageHandler::OnStartNetLog(const base::ListValue* list) {
   bool result = list->GetString(0, &log_mode_);
   DCHECK(result);
 
   if (UsingMobileUI()) {
     StartNetLog();
   } else {
-    base::FilePath home_dir = base::GetHomeDir();
-    base::FilePath default_path =
-        home_dir.Append(FILE_PATH_LITERAL("chrome-net-export-log.json"));
-    ShowSelectFileDialog(default_path);
+    base::FilePath initial_dir =
+        last_save_dir.Pointer()->empty() ? base::GetHomeDir()
+                                         : *last_save_dir.Pointer();
+    base::FilePath initial_path =
+        initial_dir.Append(FILE_PATH_LITERAL("chrome-net-export-log.json"));
+    ShowSelectFileDialog(initial_path);

[mmenke, 2016/10/24 17:04:55]

This will show the home directory every time Chrome is restarted.

What's the behavior if we just use an empty path?  On Windows, I suspect it will
show us the path wherever the last file dialog was open at, which is preserved
across browser restarts, which would probably be superior behavior.  Not sure
about other platforms, though.

[wangyix, 2016/10/24 23:35:15]

I'm working on Goobuntu, and the behavior is the following:
When the dialog is first opened after starting chrome, it defaults to listing
"recently used" folders. After the first save, it defaults to the last saved
location, as desired.  However, the last saved location is not preserved across
browser restarts.

   }
 }
 
 void NetExportMessageHandler::OnStopNetLog(const base::ListValue* list) {
   ProcessNetLogCommand(weak_ptr_factory_.GetWeakPtr(), net_log_file_writer_,
                        net_log::NetLogFileWriter::DO_STOP);
 }
 
 void NetExportMessageHandler::OnSendNetLog(const base::ListValue* list) {
   content::BrowserThread::PostTaskAndReplyWithResult(
@@ skipping 109 matching lines @@
 
   WebContents* webcontents = web_ui()->GetWebContents();
 
   select_file_dialog_ = ui::SelectFileDialog::Create(
       this, new ChromeSelectFilePolicy(webcontents));
   ui::SelectFileDialog::FileTypeInfo file_type_info;
   file_type_info.extensions = {{FILE_PATH_LITERAL("json")}};
   gfx::NativeWindow owning_window =
       webcontents ? webcontents->GetTopLevelNativeWindow()
                   : nullptr;
+
   select_file_dialog_->SelectFile(
       ui::SelectFileDialog::SELECT_SAVEAS_FILE, base::string16(), default_path,
       &file_type_info, 0, base::FilePath::StringType(), owning_window, nullptr);
 }
 
 void NetExportMessageHandler::FileSelected(const base::FilePath& path,
                                            int index,
                                            void* params) {
   select_file_dialog_ = nullptr;
+  *last_save_dir.Pointer() = path.DirName();
+
   BrowserThread::PostTaskAndReply(
       BrowserThread::FILE_USER_BLOCKING, FROM_HERE,
       base::Bind(&net_log::NetLogFileWriter::SetUpNetExportLogPath,
                  base::Unretained(net_log_file_writer_), path),
       // NetExportMessageHandler is tied to the lifetime of the tab
       // so it cannot be assured that it will be valid when this
       // StartNetLog is called. Instead of using base::Unretained a
       // weak pointer is used to adjust for this.
       base::Bind(&NetExportMessageHandler::StartNetLog,
                  weak_ptr_factory_.GetWeakPtr()));
 }
 
 void NetExportMessageHandler::FileSelectionCanceled(void* params) {
   select_file_dialog_ = nullptr;
 }
 
 }  // namespace
 
 NetExportUI::NetExportUI(content::WebUI* web_ui) : WebUIController(web_ui) {
   web_ui->AddMessageHandler(new NetExportMessageHandler());
 
   // Set up the chrome://net-export/ source.
   Profile* profile = Profile::FromWebUI(web_ui);
   content::WebUIDataSource::Add(profile, CreateNetExportHTMLSource());
 }