Add extensions_unittests to chromium_builder_tests target.

extensions/test/test_extensions_client.cc

Index: extensions/test/test_extensions_client.cc
diff --git a/extensions/test/test_extensions_client.cc b/extensions/test/test_extensions_client.cc
index c597e5a554a0a185a2c407816075509fdf4ef569..90888a76b50bbaa42f8b2133619e7785a5380c2f 100644
--- a/extensions/test/test_extensions_client.cc
+++ b/extensions/test/test_extensions_client.cc
@@ -27,12 +27,6 @@ void TestExtensionsClient::Initialize() {
   }
 }
 
-const PermissionsProvider&
-TestExtensionsClient::GetPermissionsProvider() const {
-  static TestPermissionsProvider provider;
-  return provider;
-}
-
 const PermissionMessageProvider&
 TestExtensionsClient::GetPermissionMessageProvider() const {
   static TestPermissionMessageProvider provider;