Set the Feature's ChannelForTesting to Trunk during extension tests, so that

chrome/common/extensions/manifest_tests/extension_manifests_background_unittest.cc

Index: chrome/common/extensions/manifest_tests/extension_manifests_background_unittest.cc
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_background_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_background_unittest.cc
index bb5372545395099868f649439d7969e1691a7719..874ee8c16fb95339d634fe5c7e7557dc5d8895ae 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_background_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_background_unittest.cc
@@ -11,6 +11,7 @@
 #include "chrome/common/extensions/extension.h"
 #include "chrome/common/extensions/extension_error_utils.h"
 #include "chrome/common/extensions/extension_manifest_constants.h"
+#include "chrome/common/extensions/features/feature.h"
 #include "chrome/common/extensions/features/simple_feature_provider.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -88,6 +89,7 @@ TEST_F(ExtensionManifestTest, BackgroundAllowNoJsAccess) {
 TEST_F(ExtensionManifestTest, BackgroundPageWebRequest) {
   CommandLine::ForCurrentProcess()->AppendSwitch(
       switches::kEnableExperimentalExtensionApis);
+  Feature::SetChannelForTesting(chrome::VersionInfo::CHANNEL_UNKNOWN);
 
   std::string error;
   scoped_ptr<DictionaryValue> manifest(