WebRTC: Fix and enable -Woverloaded-virtual warnings.

Essentially applying the same change as in
https://codereview.webrtc.org/2023413002 in more locations.

There's only one change affecting production code: enabling the warning
for webrtc/media:rtc_media. The rest are test changes.

With these changes, the only place the warning is disabled is in the Windows
implementation of webrtc/modules/video_capture:video_capture_internal_impl,
which is harder to fix, since it relies on sample code from the Windows SDK.

BUG=webrtc:6653
NOTRY=True

Review-Url: https://codereview.webrtc.org/2468093004
Cr-Commit-Position: refs/heads/master@{#14938}

webrtc/api/BUILD.gn

@@ -360,7 +360,6 @@ if (rtc_include_tests) {
 
     if (!is_win) {
       cflags = [ "-Wno-sign-compare" ]
-      cflags_cc = [ "-Wno-overloaded-virtual" ]
     }
   }
 

webrtc/api/peerconnection_unittest.cc

@@ -188,6 +188,13 @@ class PeerConnectionTestClient : public webrtc::PeerConnectionObserver,
                                  public ObserverInterface,
                                  public rtc::MessageHandler {
  public:
+  // We need these using declarations because there are two versions of each of
+  // the below methods and we only override one of them.
+  // TODO(deadbeef): Remove once there's only one version of the methods.
+  using PeerConnectionObserver::OnAddStream;
+  using PeerConnectionObserver::OnRemoveStream;
+  using PeerConnectionObserver::OnDataChannel;
+
   // If |config| is not provided, uses a default constructed RTCConfiguration.
   static PeerConnectionTestClient* CreateClientWithDtlsIdentityStore(
       const std::string& id,

webrtc/api/peerconnectionfactory_unittest.cc

@@ -63,6 +63,13 @@ static const char kTurnIceServerWithIPv6Address[] =
 
 class NullPeerConnectionObserver : public PeerConnectionObserver {
  public:
+  // We need these using declarations because there are two versions of each of
+  // the below methods and we only override one of them.
+  // TODO(deadbeef): Remove once there's only one version of the methods.
+  using PeerConnectionObserver::OnAddStream;
+  using PeerConnectionObserver::OnRemoveStream;
+  using PeerConnectionObserver::OnDataChannel;
+
   virtual ~NullPeerConnectionObserver() = default;
   virtual void OnMessage(const std::string& msg) {}
   virtual void OnSignalingMessage(const std::string& msg) {}

webrtc/api/peerconnectioninterface_unittest.cc

@@ -435,6 +435,13 @@ class MockTrackObserver : public ObserverInterface {
 
 class MockPeerConnectionObserver : public PeerConnectionObserver {
  public:
+  // We need these using declarations because there are two versions of each of
+  // the below methods and we only override one of them.
+  // TODO(deadbeef): Remove once there's only one version of the methods.
+  using PeerConnectionObserver::OnAddStream;
+  using PeerConnectionObserver::OnRemoveStream;
+  using PeerConnectionObserver::OnDataChannel;
+
   MockPeerConnectionObserver() : remote_streams_(StreamCollection::Create()) {}
   virtual ~MockPeerConnectionObserver() {
   }

webrtc/api/test/peerconnectiontestwrapper.h

@@ -24,6 +24,13 @@ class PeerConnectionTestWrapper
       public webrtc::CreateSessionDescriptionObserver,
       public sigslot::has_slots<> {
  public:
+  // We need these using declarations because there are two versions of each of
+  // the below methods and we only override one of them.
+  // TODO(deadbeef): Remove once there's only one version of the methods.
+  using PeerConnectionObserver::OnAddStream;
+  using PeerConnectionObserver::OnRemoveStream;
+  using PeerConnectionObserver::OnDataChannel;
+
   static void Connect(PeerConnectionTestWrapper* caller,
                       PeerConnectionTestWrapper* callee);
 

webrtc/media/BUILD.gn

@@ -28,7 +28,6 @@ config("rtc_media_warnings_config") {
   # cannot be on the target directly.
   if (!is_win) {
     cflags = [ "-Wno-deprecated-declarations" ]
-    cflags_cc = [ "-Wno-overloaded-virtual" ]
   }
 }
 
@@ -247,7 +246,6 @@ if (rtc_include_tests) {
     }
     if (!is_win) {
       cflags = [ "-Wno-sign-compare" ]
-      cflags_cc = [ "-Wno-overloaded-virtual" ]
     }
   }
 

webrtc/media/media.gyp

@@ -94,9 +94,6 @@
       'cflags!': [
         '-Wextra',
       ],
-      'cflags_cc!': [
-        '-Woverloaded-virtual',
-      ],
       'msvs_disabled_warnings': [
         4245,  # conversion from 'int' to 'size_t', signed/unsigned mismatch.
         4267,  # conversion from 'size_t' to 'int', possible loss of data.