Make sure sideload wipeout doesn't interfere with the tests.

chrome/browser/extensions/extension_browsertest.cc

Index: chrome/browser/extensions/extension_browsertest.cc
===================================================================
--- chrome/browser/extensions/extension_browsertest.cc	(revision 163351)
+++ chrome/browser/extensions/extension_browsertest.cc	(working copy)
@@ -43,6 +43,7 @@
 
 using extensions::Extension;
 using extensions::ExtensionCreator;
+using extensions::FeatureSwitch;
 
 ExtensionBrowserTest::ExtensionBrowserTest()
     : loaded_(false),
@@ -53,7 +54,9 @@
       target_visible_page_action_count_(-1),
       current_channel_(chrome::VersionInfo::CHANNEL_DEV),
       override_prompt_for_external_extensions_(
-          extensions::FeatureSwitch::prompt_for_external_extensions(), false) {
+          FeatureSwitch::prompt_for_external_extensions(), false),
+       override_sideload_wipeout_(
+          FeatureSwitch::sideload_wipeout(), false) {
   EXPECT_TRUE(temp_dir_.CreateUniqueTempDir());
 }