Remove unused (dead) friend-declaration in ResourceClient

SVGElementProxy no longer exist.

Change-Id: I552e9d3d0d092ba5d0c51c8bacc8b27bdf29fe4c
Reviewed-on: https://chromium-review.googlesource.com/1105977Reviewed-by: Nate Chapin <japhet@chromium.org>
Commit-Queue: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#568971}

third_party/blink/renderer/platform/loader/fetch/resource_client.h

@@ -81,11 +81,6 @@ class PLATFORM_EXPORT ResourceClient : public GarbageCollectedMixin {
   // non-null Resource*. ResourceClient subclasses are responsible for calling
   // ClearResource().
   friend class ResourceFetcher;
-  // TODO(japhet): There isn't a clean way for SVGResourceClients to determine
-  // whether SVGElementProxy is holding a Resource that it should register with,
-  // so SVGElementProxy handles it for those clients. SVGResourceClients should
-  // have a better way to register themselves as clients. crbug.com/789198
-  friend class SVGElementProxy;
   // CSSFontFaceSrcValue only ever requests a Resource once, and acts as an
   // intermediate caching layer of sorts. It needs to be able to register
   // additional clients.