Make CFWL_WidgetMgr{Delegate} inherit from IFWL_WidgetMgr{Delegate}.

Make CFWL_WidgetMgr{Delegate} inherit from IFWL_WidgetMgr{Delegate}.

C-style casting masked a fairly serious botch, where an
CFWL_ type would get cast to an IFWL_ type, and later we'd
invoke virtual methods against the IFWL_ type. Without the
proper inheritance, there's no reason to believe that the
vtables for each of these would line up with each other.

Fixing the inheritence allows us to remove the c-style casts.
I'm guessing these were added to make this compile without
having to understand the true nature of the flaw.

R=thestig@chromium.org

Committed: https://pdfium.googlesource.com/pdfium/+/e8131137dabd2e1dcf1bcdf49e81ee6c9ae26413

[Tom Sepez, 2015-11-13 01:18:47]

tsepez@chromium.org changed reviewers:
+ thestig@chromium.org

[Tom Sepez, 2015-11-13 01:18:47]

Lei, there are a pile of these, if one greps for IFWL_ types that don't appear
as superclasses.

[Lei Zhang, 2015-11-13 05:09:09]

lgtm

[Tom Sepez, 2015-11-13 18:14:22]

Committed patchset #2 (id:20001) manually as
e8131137dabd2e1dcf1bcdf49e81ee6c9ae26413 (presubmit successful).