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

chrome/browser/download/download_manager.h

Index: chrome/browser/download/download_manager.h
diff --git a/chrome/browser/download/download_manager.h b/chrome/browser/download/download_manager.h
index e072d42498fcd2310388d3f879e2b1c0f4798f8d..4a5814bb62ea33c4bdc98b1dfec2d2222f197eaf 100644
--- a/chrome/browser/download/download_manager.h
+++ b/chrome/browser/download/download_manager.h
@@ -86,7 +86,9 @@ class DownloadManager
     // Called immediately after the DownloadManager puts up a select file
     // dialog.
     // |id| indicates which download opened the dialog.
-    virtual void SelectFileDialogDisplayed(int32 id) {}
+    // |suggested_path| indicates the path suggested in the dialog.
+    virtual void SelectFileDialogDisplayed(
+        int32 id, const FilePath& suggested_path) {}
 
    protected:
     virtual ~Observer() {}
@@ -251,6 +253,17 @@ class DownloadManager
   // For debugging.
   void AssertNotInQueues(DownloadItem* download);
 
+  // Chooses a writable directory from |website_save_dir|, |download_save_dir|
+  // and |default_download_dir| in this order of priority.
+  // If none of them is writable, creates |download_save_dir| and
+  // chooses |download_save_dir|. The choosed directory is stored to |save_dir|.
+  // Returns true if neither |website_save_dir| nor |download_save_dir|
+  // is writable, which indicates the select file dialog should be displayed.
+  static bool ChooseSavableDirectory(const FilePath& website_save_dir,
+                                     const FilePath& download_save_dir,
+                                     const FilePath& default_download_dir,
+                                     FilePath* save_dir);
+
  private:
   // For testing.
   friend class DownloadManagerTest;
@@ -288,7 +301,8 @@ class DownloadManager
   // stalls from interacting with the file system.
   void CheckIfSuggestedPathExists(int32 download_id,
                                   DownloadStateInfo state,
-                                  const FilePath& default_path);
+                                  const FilePath& download_save_dir,
+                                  const FilePath& default_download_dir);
 
   // Called on the UI thread once the DownloadManager has determined whether the
   // suggested file path exists.