diff --git a/gfx/2d/DrawTargetSkia.cpp b/gfx/2d/DrawTargetSkia.cpp
index e9a2bc418b46..2395d9cce2e6 100644
--- a/gfx/2d/DrawTargetSkia.cpp
+++ b/gfx/2d/DrawTargetSkia.cpp
@@ -1948,9 +1948,9 @@ public:
     : SkImageFilter(nullptr, 0, nullptr)
   {}
 
-  virtual sk_sp<SkSpecialImage> onFilterImage(SkSpecialImage* source,
-                                              const Context& ctx,
-                                              SkIPoint* offset) const override {
+  sk_sp<SkSpecialImage> onFilterImage(SkSpecialImage* source,
+                                      const Context& ctx,
+                                      SkIPoint* offset) const override {
     offset->set(0, 0);
     return sk_ref_sp(source);
   }
diff --git a/gfx/2d/JobScheduler_posix.cpp b/gfx/2d/JobScheduler_posix.cpp
index fcbdca820442..01a81c21407c 100644
--- a/gfx/2d/JobScheduler_posix.cpp
+++ b/gfx/2d/JobScheduler_posix.cpp
@@ -21,12 +21,12 @@ public:
     pthread_create(&mThread, nullptr, ThreadCallback, static_cast<WorkerThread*>(this));
   }
 
-  ~WorkerThreadPosix()
+  ~WorkerThreadPosix() override
   {
     pthread_join(mThread, nullptr);
   }
 
-  virtual void SetName(const char*) override
+  void SetName(const char*) override
   {
 // XXX - temporarily disabled, see bug 1209039
 //
diff --git a/gfx/layers/LayerTreeInvalidation.cpp b/gfx/layers/LayerTreeInvalidation.cpp
index 5604fafee344..a5fdb2df008c 100644
--- a/gfx/layers/LayerTreeInvalidation.cpp
+++ b/gfx/layers/LayerTreeInvalidation.cpp
@@ -157,7 +157,7 @@ struct LayerPropertiesBase : public LayerProperties
   {
     MOZ_COUNT_CTOR(LayerPropertiesBase);
   }
-  ~LayerPropertiesBase()
+  ~LayerPropertiesBase() override
   {
     MOZ_COUNT_DTOR(LayerPropertiesBase);
   }
@@ -167,11 +167,11 @@ protected:
   LayerPropertiesBase& operator=(const LayerPropertiesBase& a) = delete;
 
 public:
-  virtual nsIntRegion ComputeDifferences(Layer* aRoot,
-                                         NotifySubDocInvalidationFunc aCallback,
-                                         bool* aGeometryChanged);
+  nsIntRegion ComputeDifferences(Layer* aRoot,
+                                 NotifySubDocInvalidationFunc aCallback,
+                                 bool* aGeometryChanged) override;
 
-  virtual void MoveBy(const IntPoint& aOffset);
+  void MoveBy(const IntPoint& aOffset) override;
 
   nsIntRegion ComputeChange(NotifySubDocInvalidationFunc aCallback,
                             bool& aGeometryChanged)
@@ -454,8 +454,8 @@ protected:
   ColorLayerProperties& operator=(const ColorLayerProperties& a) = delete;
 
 public:
-  virtual nsIntRegion ComputeChangeInternal(NotifySubDocInvalidationFunc aCallback,
-                                            bool& aGeometryChanged)
+  nsIntRegion ComputeChangeInternal(NotifySubDocInvalidationFunc aCallback,
+                                    bool& aGeometryChanged) override
   {
     ColorLayer* color = static_cast<ColorLayer*>(mLayer.get());
 
@@ -505,8 +505,8 @@ struct ImageLayerProperties : public LayerPropertiesBase
     }
   }
 
-  virtual nsIntRegion ComputeChangeInternal(NotifySubDocInvalidationFunc aCallback,
-                                            bool& aGeometryChanged)
+  nsIntRegion ComputeChangeInternal(NotifySubDocInvalidationFunc aCallback,
+                                    bool& aGeometryChanged) override
   {
     ImageLayer* imageLayer = static_cast<ImageLayer*>(mLayer.get());
 
@@ -566,8 +566,8 @@ struct CanvasLayerProperties : public LayerPropertiesBase
     mFrameID = mImageHost ? mImageHost->GetFrameID() : -1;
   }
 
-  virtual nsIntRegion ComputeChangeInternal(NotifySubDocInvalidationFunc aCallback,
-                                            bool& aGeometryChanged)
+  nsIntRegion ComputeChangeInternal(NotifySubDocInvalidationFunc aCallback,
+                                    bool& aGeometryChanged) override
   {
     CanvasLayer* canvasLayer = static_cast<CanvasLayer*>(mLayer.get());
 
diff --git a/gfx/layers/basic/BasicImageLayer.cpp b/gfx/layers/basic/BasicImageLayer.cpp
index 0bb6b132d091..6e69bfe2e2d0 100644
--- a/gfx/layers/basic/BasicImageLayer.cpp
+++ b/gfx/layers/basic/BasicImageLayer.cpp
@@ -31,24 +31,24 @@ public:
     MOZ_COUNT_CTOR(BasicImageLayer);
   }
 protected:
-  virtual ~BasicImageLayer()
+  ~BasicImageLayer() override
   {
     MOZ_COUNT_DTOR(BasicImageLayer);
   }
 
 public:
-  virtual void SetVisibleRegion(const LayerIntRegion& aRegion) override
+  void SetVisibleRegion(const LayerIntRegion& aRegion) override
   {
     NS_ASSERTION(BasicManager()->InConstruction(),
                  "Can only set properties in construction phase");
     ImageLayer::SetVisibleRegion(aRegion);
   }
 
-  virtual void Paint(DrawTarget* aDT,
-                     const gfx::Point& aDeviceOffset,
-                     Layer* aMaskLayer) override;
+  void Paint(DrawTarget* aDT,
+             const gfx::Point& aDeviceOffset,
+             Layer* aMaskLayer) override;
 
-  virtual already_AddRefed<SourceSurface> GetAsSourceSurface() override;
+  already_AddRefed<SourceSurface> GetAsSourceSurface() override;
 
 protected:
   BasicLayerManager* BasicManager()
diff --git a/gfx/thebes/gfxDrawable.cpp b/gfx/thebes/gfxDrawable.cpp
index b52bd9718b06..cf6c2d8c7609 100644
--- a/gfx/thebes/gfxDrawable.cpp
+++ b/gfx/thebes/gfxDrawable.cpp
@@ -190,12 +190,12 @@ public:
         NS_ASSERTION(aDrawable, "aDrawable is null!");
     }
 
-    virtual ~DrawingCallbackFromDrawable() = default;
+    ~DrawingCallbackFromDrawable() override = default;
 
-    virtual bool operator()(gfxContext* aContext,
-                              const gfxRect& aFillRect,
-                              const SamplingFilter aSamplingFilter,
-                              const gfxMatrix& aTransform = gfxMatrix())
+    bool operator()(gfxContext* aContext,
+                    const gfxRect& aFillRect,
+                    const SamplingFilter aSamplingFilter,
+                    const gfxMatrix& aTransform = gfxMatrix()) override
     {
         return mDrawable->Draw(aContext, aFillRect, ExtendMode::CLAMP,
                                aSamplingFilter, 1.0,
diff --git a/gfx/thebes/gfxPlatform.cpp b/gfx/thebes/gfxPlatform.cpp
index 127326429dcd..afe7d614cbac 100644
--- a/gfx/thebes/gfxPlatform.cpp
+++ b/gfx/thebes/gfxPlatform.cpp
@@ -195,11 +195,11 @@ class CrashStatsLogForwarder: public mozilla::gfx::LogForwarder
 {
 public:
   explicit CrashStatsLogForwarder(const char* aKey);
-  virtual void Log(const std::string& aString) override;
-  virtual void CrashAction(LogReason aReason) override;
-  virtual bool UpdateStringsVector(const std::string& aString) override;
+  void Log(const std::string& aString) override;
+  void CrashAction(LogReason aReason) override;
+  bool UpdateStringsVector(const std::string& aString) override;
 
-  virtual LoggingRecord LoggingRecordCopy() override;
+  LoggingRecord LoggingRecordCopy() override;
 
   void SetCircularBufferSize(uint32_t aCapacity);
 
@@ -307,7 +307,7 @@ void CrashStatsLogForwarder::UpdateCrashReport()
 
 class LogForwarderEvent : public Runnable
 {
-  virtual ~LogForwarderEvent() = default;
+  ~LogForwarderEvent() override = default;
 
   NS_DECL_ISUPPORTS_INHERITED
 
@@ -361,7 +361,7 @@ void CrashStatsLogForwarder::Log(const std::string& aString)
 
 class CrashTelemetryEvent : public Runnable
 {
-  virtual ~CrashTelemetryEvent() = default;
+  ~CrashTelemetryEvent() override = default;
 
   NS_DECL_ISUPPORTS_INHERITED
 
diff --git a/gfx/thebes/gfxPlatformMac.cpp b/gfx/thebes/gfxPlatformMac.cpp
index 9e957ca673b6..e8189accc905 100644
--- a/gfx/thebes/gfxPlatformMac.cpp
+++ b/gfx/thebes/gfxPlatformMac.cpp
@@ -400,7 +400,7 @@ public:
   {
   }
 
-  virtual Display& GetGlobalDisplay() override
+  Display& GetGlobalDisplay() override
   {
     return mGlobalDisplay;
   }
@@ -415,7 +415,7 @@ public:
       mTimer = do_CreateInstance(NS_TIMER_CONTRACTID);
     }
 
-    ~OSXDisplay()
+    ~OSXDisplay() override
     {
       MOZ_ASSERT(NS_IsMainThread());
     }
@@ -428,7 +428,7 @@ public:
       osxDisplay->EnableVsync();
     }
 
-    virtual void EnableVsync() override
+    void EnableVsync() override
     {
       MOZ_ASSERT(NS_IsMainThread());
       if (IsVsyncEnabled()) {
@@ -488,7 +488,7 @@ public:
       }
     }
 
-    virtual void DisableVsync() override
+    void DisableVsync() override
     {
       MOZ_ASSERT(NS_IsMainThread());
       if (!IsVsyncEnabled()) {
@@ -502,18 +502,18 @@ public:
       }
     }
 
-    virtual bool IsVsyncEnabled() override
+    bool IsVsyncEnabled() override
     {
       MOZ_ASSERT(NS_IsMainThread());
       return mDisplayLink != nullptr;
     }
 
-    virtual TimeDuration GetVsyncRate() override
+    TimeDuration GetVsyncRate() override
     {
       return mVsyncRate;
     }
 
-    virtual void Shutdown() override
+    void Shutdown() override
     {
       MOZ_ASSERT(NS_IsMainThread());
       mTimer->Cancel();
@@ -536,7 +536,7 @@ public:
   }; // OSXDisplay
 
 private:
-  virtual ~OSXVsyncSource() = default;
+  ~OSXVsyncSource() override = default;
 
   OSXDisplay mGlobalDisplay;
 }; // OSXVsyncSource