Resolve enum value collision on UseCounter.h

r184341 and r184316 both added a new use counter with enum value 574.
This CL resolves the collision.

BUG=None

Review URL: https://codereview.chromium.org/684783003

git-svn-id: svn://svn.chromium.org/blink/trunk@184534 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[ServiceWorker] Fix ResourceFetcher::isControlledByServiceWorker to support HTMLImports.

While loading the resources from the imported HTML, ResourceFetcher's m_documentLoader is NULL.
In such cases whether the request is controlled by ServiceWorker or not is determined by the document loader of the frame.
But in current code ResourceFetcher::isControlledByServiceWorker() always returns false.

This patch fixes this by checking the document loader of the frame.

BUG=427136

Review URL: https://codereview.chromium.org/655373003

git-svn-id: svn://svn.chromium.org/blink/trunk@184535 bbb929c8-8fbe-4397-9dbb-9b2b20218538