Oilpan: reliably track listening PlatformEventControllers.
Turn PlatformEventController into a GC mixin with Oilpan enabled, and
have the PlatformEventDispatcher instance track those via a Persistent
reference.
It seems precarious to rely on the controller lifetimes be maintained by
way of other references 'long enough' for the embedder's platform event
handling layer.
R=mlamouri,mkwst,haraken,timvolodine
BUG=419515
Review URL: https://codereview.chromium.org/618673002
git-svn-id: svn://svn.chromium.org/blink/trunk@183158 bbb929c8-8fbe-4397-9dbb-9b2b20218538
8 files changed
