pdfium: Fix all -Wdelete-non-virtual-dtor violations on Mac.

pdfium: Fix all -Wdelete-non-virtual-dtor violations on Mac.

Calling `delete` on an object of a type that has virtual functions but
not a virtual destructor is questionable: Since the object has virtual functions,
it likely has subclasses, so if it's deleted through the base pointer and the
destructor isn't virtual, the subclass destructor won't be called.

In most cases, the classes getting deleted can just be marked final to tell
the compiler that it can't possibly have subclasses (this also enables the
compiler to generate better code).

Two classes didn't have any sub- or superclasses but virtual functions -
this doesn't make sense, so make all methods of these classes non-virtual.
(Also delete an unused function on one of the two classes.)

In one case, a class actually did have a subclass that needs to be deleted
virtually, so mark one destructor as virtual.

BUG=none
R=bo_xu@foxitsoftware.com

Committed: https://pdfium.googlesource.com/pdfium/+/5eb9f7b

[Nico, 2014-07-05 03:29:13]

The direct motivation was that this warning isn't disabled for some reason on
the clang/win bot (
http://build.chromium.org/p/chromium.fyi/builders/Chromium%20Win%20Clang%20%2...
) and makes the build output fairly noisy.

While working on this, I built pdfium with -Wall and found many scary warnings.
One example that looks like a bug:
../../third_party/pdfium/fpdfsdk/src/formfiller/../../include/formfiller/../pdfwindow/PWL_ComboBox.h:26:21:
warning: 'CPWL_CBListBox::OnKeyDown' hides overloaded virtual function
[-Woverloaded-virtual]
        virtual FX_BOOL                         OnKeyDown(FX_WORD nChar, FX_BOOL
& bExit, FX_DWORD nFlag);
                                                ^
../../third_party/pdfium/fpdfsdk/src/formfiller/../../include/formfiller/../pdfwindow/PWL_ListBox.h:49:22:
note: hidden overloaded virtual function 'CPWL_ListBox::OnKeyDown' declared
here: different number of parameters (2 vs 3)
        virtual FX_BOOL                                 OnKeyDown(FX_WORD nChar,
FX_DWORD nFlag);
                                                        ^


So I think a good goal would be to fix most -Wall warnings in pdfium; this is a
start.

https://codereview.chromium.org/370853002/diff/1/fpdfsdk/src/fpdfeditpage.cpp
File fpdfsdk/src/fpdfeditpage.cpp (right):

https://codereview.chromium.org/370853002/diff/1/fpdfsdk/src/fpdfeditpage.cpp...
fpdfsdk/src/fpdfeditpage.cpp:330: }
(Also fix a -Wnewline warning while here.)

[jam, 2014-07-14 22:49:08]

rerouting to Bo/Jun

[Nico, 2014-07-15 21:45:24]

Bo/Jun: Ping.

[Bo Xu, 2014-07-15 22:11:15]

On 2014/07/15 21:45:24, Nico (away) wrote:
> Bo/Jun: Ping.

I am looking at this one.

[Nico, 2014-07-16 20:50:03]

On 2014/07/15 22:11:15, Bo Xu wrote:
> On 2014/07/15 21:45:24, Nico (away) wrote:
> > Bo/Jun: Ping.
> 
> I am looking at this one.

Thanks! I uploaded a rebased version (see patch set 2) that applies cleanly on
master.

[Bo Xu, 2014-07-16 20:55:59]

On 2014/07/16 20:50:03, Nico (away) wrote:
> On 2014/07/15 22:11:15, Bo Xu wrote:
> > On 2014/07/15 21:45:24, Nico (away) wrote:
> > > Bo/Jun: Ping.
> > 
> > I am looking at this one.
> 
> Thanks! I uploaded a rebased version (see patch set 2) that applies cleanly on
> master.

Got it. I am re-routing this to developers that are more familiar with this
part. I will update whenever I hear back.

[Bo Xu, 2014-07-18 02:17:48]

lgtm

[Nico, 2014-07-18 16:14:39]

Committed patchset #2 manually as r5eb9f7b (presubmit successful).