Use a temp directory for downloads in WebstoreInstaller tests.

chrome/browser/extensions/webstore_installer_test.cc

Index: chrome/browser/extensions/webstore_installer_test.cc
diff --git a/chrome/browser/extensions/webstore_installer_test.cc b/chrome/browser/extensions/webstore_installer_test.cc
index fdc4d4a4a64f3b656eab3cc2c3acf3903a3eaae1..ff3db722597b6dc84f05ba578eee7d834542ff6d 100644
--- a/chrome/browser/extensions/webstore_installer_test.cc
+++ b/chrome/browser/extensions/webstore_installer_test.cc
@@ -5,6 +5,7 @@
 #include "base/command_line.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
+#include "chrome/browser/download/download_prefs.h"
 #include "chrome/browser/extensions/extension_install_prompt.h"
 #include "chrome/browser/extensions/tab_helper.h"
 #include "chrome/browser/extensions/webstore_inline_installer.h"
@@ -77,6 +78,14 @@ void WebstoreInstallerTest::SetUpInProcessBrowserTestFixture() {
   host_resolver()->AddRule(unverified_domain_, "127.0.0.1");
 }
 
+void WebstoreInstallerTest::SetUpOnMainThread() {
+  InProcessBrowserTest::SetUpOnMainThread();
+  ASSERT_TRUE(download_directory_.CreateUniqueTempDir());
+  DownloadPrefs* download_prefs = DownloadPrefs::FromBrowserContext(
+      browser()->profile());
+  download_prefs->SetDownloadPath(download_directory_.path());
+}
+
 GURL WebstoreInstallerTest::GenerateTestServerUrl(
     const std::string& domain,
     const std::string& page_filename) {