Begin to enable extension APIs in Extension Service Worker.

chrome/common/extensions/chrome_extensions_client.cc

Index: chrome/common/extensions/chrome_extensions_client.cc
diff --git a/chrome/common/extensions/chrome_extensions_client.cc b/chrome/common/extensions/chrome_extensions_client.cc
index 14f7f88de594cfcc48b5dd01c1030694732bb07e..a04964158106ff3b5dc058ae35bdea34f6e5867d 100644
--- a/chrome/common/extensions/chrome_extensions_client.cc
+++ b/chrome/common/extensions/chrome_extensions_client.cc
@@ -378,6 +378,11 @@ std::set<base::FilePath> ChromeExtensionsClient::GetBrowserImagePaths(
   return image_paths;
 }
 
+bool ChromeExtensionsClient::ExtensionAPIEnabledInExtensionServiceWorkers()
+    const {
+  return GetCurrentChannel() == version_info::Channel::UNKNOWN;
+}
+
 // static
 ChromeExtensionsClient* ChromeExtensionsClient::GetInstance() {
   return g_client.Pointer();