Disable VS 2015 warning that fires on compiler-generated constructors.

Disable VS 2015 warning that fires on compiler-generated constructors.

C4589 fires when a derived class illegally calls the constructor for
its virtual base class. Unfortunately it fires inappropriately.

If Base has a pure-virtual function and Derived is dllexported and
derives virtually from the base class then the compiler-generated
copy constructor will illegally initialize the virtual base class.
The warning is:
warning C4589 : Constructor of abstract class 'Derived' ignores
initializer for virtual base class 'Base'
  note : This diagnostic occurred in the compiler generated function
'Derived::Derived(const Derived &)'

While this warning can be potentially useful (it found bad code in
crbug.com/510497) it mostly fires inappropriately. Here is repro code:

class __declspec(dllexport) Base {
  virtual void SomeFunction() = 0;
};

class __declspec(dllexport) Derived : virtual public Base {
  // Deleting the assignment operator avoids the warning
  //Derived(const Derived&) = delete;

  // Overriding SomeFunction avoids the warning
  //void SomeFunction() override {};
};

The bug has been reported.

R=thakis@chromium.org
BUG=440500
Committed: https://crrev.com/d5b9a8565675b8969dd34b6aa765adcd443b5527
Cr-Commit-Position: refs/heads/master@{#338964}

[Nico, 2015-07-15 22:46:25]

Does build/config/compiler/BUILD.gn need this too? Or is gn explicitly out of
scope for 2015 work for now? (Probably easier to fix both places at once instead
of doing everything in gyp, forgetting everything, and then paging it all back
in to do gn?)

[brucedawson, 2015-07-15 22:50:24]

Good point. This should be done in gn as well. Please hold...

[brucedawson, 2015-07-15 23:03:42]

Added to .gn configuration and sorted.

[brucedawson, 2015-07-15 23:05:25]

Added to gn. Full testing is not possible because gn doesn't support building
from an installed VS instance, but the gn change works with VS 2013 and will be
ready for VS 2015.

I also realized that the warning numbers are supposed to be sorted, so I fixed
that in common.gypi.

[Nico, 2015-07-15 23:06:06]

lgtm

[brucedawson, 2015-07-15 23:09:32]

The CQ bit was checked by brucedawson@chromium.org

[commit-bot: I haz the power, 2015-07-15 23:10:59]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1234253003/40001

[commit-bot: I haz the power, 2015-07-16 00:43:57]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-07-16 00:45:01]

Patchset 3 (id:??) landed as
https://crrev.com/d5b9a8565675b8969dd34b6aa765adcd443b5527
Cr-Commit-Position: refs/heads/master@{#338964}

[brucedawson, 2015-07-23 23:24:29]

Microsoft has acknowledged this bug
(http://connect.microsoft.com/VisualStudio/feedback/details/1570496/vs-2015-ge...)
and has said that it will be fixed in the next update of VS 2015. Specifically
they said:

"Thank you for reporting this issue; it will be fixed in the Update 1 release of
VS2015.

It's far from ideal, but besides disabling the warning or defining Derived's
copy and/or move constructors as deleted, the workaround is to explicitly define
copy and/or move constructors for Derived that don't initialize Base."