Bug 1540581 - P6. Tidy some C++ declarations in gfx/. r=gerald,jrmuizel

* Remove redundant virtual keywords
* Mark all destructors of inheriting classes as virtual for clarity
* Mark all classes without virtual destructor as final (exposed errors)
* Make destructor virtual where it needed to be (some were missing)
* Replace empty ({}) code declaration in header with = default
* Remove virtual unused methods

I probably missed some, it quickly became a rabbit hole.

Differential Revision: https://phabricator.services.mozilla.com/D26060

gfx/layers/LayerScope.cpp

@@ -147,7 +147,7 @@ class LayerScopeWebSocketManager {
     }
 
    private:
-    virtual ~SocketListener() {}
+    virtual ~SocketListener() = default;
   };
 
   /*
@@ -380,7 +380,7 @@ class DebugGLData : public LinkedListElement<DebugGLData> {
  public:
   explicit DebugGLData(Packet::DataType aDataType) : mDataType(aDataType) {}
 
-  virtual ~DebugGLData() {}
+  virtual ~DebugGLData() = default;
 
   virtual bool Write() = 0;
 
@@ -405,7 +405,7 @@ class DebugGLFrameStatusData final : public DebugGLData {
   explicit DebugGLFrameStatusData(Packet::DataType aDataType)
       : DebugGLData(aDataType), mFrameStamp(0) {}
 
-  virtual bool Write() override {
+  bool Write() override {
     Packet packet;
     packet.set_type(mDataType);
 
@@ -441,7 +441,7 @@ class DebugGLTextureData final : public DebugGLData {
     pack(img);
   }
 
-  virtual bool Write() override { return WriteToStream(*mPacket); }
+  bool Write() override { return WriteToStream(*mPacket); }
 
  private:
   void pack(DataSourceSurface* aImage) {
@@ -507,7 +507,7 @@ class DebugGLColorData final : public DebugGLData {
         mColor(color.ToABGR()),
         mSize(width, height) {}
 
-  virtual bool Write() override {
+  bool Write() override {
     Packet packet;
     packet.set_type(mDataType);
 
@@ -531,7 +531,7 @@ class DebugGLLayersData final : public DebugGLData {
   explicit DebugGLLayersData(UniquePtr<Packet> aPacket)
       : DebugGLData(Packet::LAYERS), mPacket(std::move(aPacket)) {}
 
-  virtual bool Write() override {
+  bool Write() override {
     mPacket->set_type(mDataType);
     return WriteToStream(*mPacket);
   }
@@ -548,7 +548,7 @@ class DebugGLMetaData final : public DebugGLData {
   explicit DebugGLMetaData(Packet::DataType aDataType)
       : DebugGLData(aDataType), mComposedByHwc(false) {}
 
-  virtual bool Write() override {
+  bool Write() override {
     Packet packet;
     packet.set_type(mDataType);
 
@@ -581,7 +581,7 @@ class DebugGLDrawData final : public DebugGLData {
     }
   }
 
-  virtual bool Write() override {
+  bool Write() override {
     Packet packet;
     packet.set_type(mDataType);
 
@@ -640,7 +640,7 @@ class DebugDataSender {
     }
 
    private:
-    virtual ~AppendTask() {}
+    virtual ~AppendTask() = default;
 
     DebugGLData* mData;
     // Keep a strong reference to DebugDataSender to prevent this object
@@ -661,7 +661,7 @@ class DebugDataSender {
     }
 
    private:
-    virtual ~ClearTask() {}
+    virtual ~ClearTask() = default;
 
     RefPtr<DebugDataSender> mHost;
   };
@@ -691,7 +691,7 @@ class DebugDataSender {
     }
 
    private:
-    virtual ~SendTask() {}
+    virtual ~SendTask() = default;
 
     RefPtr<DebugDataSender> mHost;
   };
@@ -707,7 +707,7 @@ class DebugDataSender {
   void Send() { mThread->Dispatch(new SendTask(this), NS_DISPATCH_NORMAL); }
 
  protected:
-  virtual ~DebugDataSender() {}
+  virtual ~DebugDataSender() = default;
   void RemoveData() {
     MOZ_ASSERT(mThread->SerialEventTarget()->IsOnCurrentThread());
     if (mList.isEmpty()) return;