FunctionTemplateInfo::SetPrototypeProviderTemplate adds support for sharing
prototypes between several function templates. This is used to properly set up
Image.prototype and HTMLImageElement.protoype which should be equal according
to the spec.

BUG=chromium:2969

Review-Url: https://codereview.chromium.org/2531653002
Cr-Commit-Position: refs/heads/master@{#41343}