ContentProviderDependencyHelper is causing lock contention in StructureMap

Description

ContentProviderDependencyHelper is wrapped by an Injected<T>. Due to heavy usage in ContentProviderBase, many calls are being made to StructureMap, causing lock contention. In some cases, this issue caused a site to effectively hang when too many threads are trying to get instances of this class from StructureMap.

NOTE: This fix removes the wrapping Injected<T> on the INTERNAL API DependencyHelper on the Content Provider base class. If you used this API, you need to modify your code.