When the download folder does not exist, change the download folder to a user's "Downloads"

chrome/browser/ui/webui/options/advanced_options_handler.cc

Index: chrome/browser/ui/webui/options/advanced_options_handler.cc
diff --git a/chrome/browser/ui/webui/options/advanced_options_handler.cc b/chrome/browser/ui/webui/options/advanced_options_handler.cc
index dce0eadbf31ba4d20e81ab2f4d1fd9a6de269cc5..be42c60b7e3140a6d884aef254b1ecea8b49f014 100644
--- a/chrome/browser/ui/webui/options/advanced_options_handler.cc
+++ b/chrome/browser/ui/webui/options/advanced_options_handler.cc
@@ -9,6 +9,8 @@
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/command_line.h"
+#include "base/file_util.h"
+#include "base/path_service.h"
 #include "base/utf_string_conversions.h"
 #include "base/values.h"
 #include "chrome/browser/browser_process.h"
@@ -24,6 +26,7 @@
 #include "chrome/browser/service/service_process_control.h"
 #include "chrome/browser/ui/options/options_util.h"
 #include "chrome/common/chrome_notification_types.h"
+#include "chrome/common/chrome_paths.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/common/url_constants.h"
@@ -201,6 +204,9 @@ void AdvancedOptionsHandler::Initialize() {
   SetupMetricsReportingSettingVisibility();
   SetupFontSizeLabel();
   SetupDownloadLocationPath();
+  download_path_checker_ = new DownloadPathChecker(this);
+  download_path_checker_->CheckIfDownloadPathExists(
+      default_download_location_.GetValue());
   SetupPromptForDownload();
   SetupAutoOpenFileTypesDisabledAttribute();
   SetupProxySettingsSection();
@@ -661,3 +667,49 @@ void AdvancedOptionsHandler::SetupSSLConfigSettings() {
         "options.AdvancedOptions.SetUseTLS1CheckboxState", checked, disabled);
   }
 }
+
+AdvancedOptionsHandler::DownloadPathChecker::DownloadPathChecker(
+    AdvancedOptionsHandler* handler)
+    : handler_(handler) {
+}
+
+AdvancedOptionsHandler::DownloadPathChecker::~DownloadPathChecker() {
+}
+
+void AdvancedOptionsHandler::DownloadPathChecker::
+                             CheckIfDownloadPathExists(const FilePath& path) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  BrowserThread::PostTask(BrowserThread::FILE, FROM_HERE,
+      NewRunnableMethod(this,
+          &DownloadPathChecker::CheckIfDownloadPathExistsOnFileThread, path));
+}
+
+void AdvancedOptionsHandler::DownloadPathChecker::
+                             CheckIfDownloadPathExistsOnFileThread(
+                                 const FilePath& path) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  if (!file_util::PathExists(path)) {
+    FilePath new_path;
+    if (!PathService::Get(chrome::DIR_DEFAULT_DOWNLOADS, &new_path)) {
+      // Create the |path| folder if we cannot get DIR_DEFAULT_DOWNLOADS
+      // (This will be a rare case).
+      new_path = path;
+    }
+    // Make sure that the folder does exist.
+    if (!file_util::CreateDirectory(new_path))
+      LOG(ERROR) << "Failed to create " << new_path.value();
+
+    BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
+        NewRunnableMethod(this,
+            &DownloadPathChecker::OnDownloadPathChanged, new_path));
+  }
+}
+
+void AdvancedOptionsHandler::DownloadPathChecker::
+                             OnDownloadPathChanged(const FilePath path) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  if (handler_) {
+    handler_->default_download_location_.SetValue(path);
+    handler_->SetupDownloadLocationPath();
+  }
+}