Use the user's preferred downloads directory for creating the initial download file.

content/browser/download/base_file.cc

Index: content/browser/download/base_file.cc
diff --git a/content/browser/download/base_file.cc b/content/browser/download/base_file.cc
index 1d5d1e2e1ba3318bd7ae74a51a152d1d9508acbe..13920fe0b59788b1012b8e169a72a6b16abfa16d 100644
--- a/content/browser/download/base_file.cc
+++ b/content/browser/download/base_file.cc
@@ -15,7 +15,6 @@
 #include "content/browser/download/download_net_log_parameters.h"
 #include "content/browser/download/download_stats.h"
 #include "content/public/browser/browser_thread.h"
-#include "content/public/browser/content_browser_client.h"
 #include "crypto/secure_hash.h"
 #include "net/base/file_stream.h"
 #include "net/base/net_errors.h"
@@ -203,7 +202,8 @@ net::Error RenameFileAndResetSecurityDescriptor(
 // This will initialize the entire array to zero.
 const unsigned char BaseFile::kEmptySha256Hash[] = { 0 };
 
-BaseFile::BaseFile(const FilePath& full_path,
+BaseFile::BaseFile(const FilePath& download_directory,
+                   const FilePath& full_path,
                    const GURL& source_url,
                    const GURL& referrer_url,
                    int64 received_bytes,
@@ -211,7 +211,8 @@ BaseFile::BaseFile(const FilePath& full_path,
                    const std::string& hash_state,
                    const linked_ptr<net::FileStream>& file_stream,
                    const net::BoundNetLog& bound_net_log)
-    : full_path_(full_path),
+    : download_directory_(download_directory),
+      full_path_(full_path),
       source_url_(source_url),
       referrer_url_(referrer_url),
       file_stream_(file_stream),
@@ -248,12 +249,11 @@ BaseFile::~BaseFile() {
 net::Error BaseFile::Initialize() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   DCHECK(!detached_);
+  DCHECK(!full_path_.empty() || !download_directory_.empty());
 
   if (full_path_.empty()) {
     FilePath temp_file;
-    FilePath download_dir =
-        content::GetContentClient()->browser()->GetDefaultDownloadDirectory();
-    if (!file_util::CreateTemporaryFileInDir(download_dir, &temp_file) &&
+    if (!file_util::CreateTemporaryFileInDir(download_directory_, &temp_file) &&
         !file_util::CreateTemporaryFile(&temp_file)) {
       return LOG_ERROR("unable to create", net::ERR_FILE_NOT_FOUND);
     }