Add IsHidden to CompositorWidget. (bug 1365879 part 10, r=rhunt)

gfx/layers/d3d11/CompositorD3D11.cpp

@@ -967,7 +967,7 @@ CompositorD3D11::BeginFrame(const nsIntRegion& aInvalidRegion,
   // this is important because resizing our buffers when mimised will fail and
   // cause a crash when we're restored.
   NS_ASSERTION(mHwnd, "Couldn't find an HWND when initialising?");
-  if (::IsIconic(mHwnd)) {
+  if (mWidget->IsHidden()) {
     // We are not going to render, and not going to call EndFrame so we have to
     // read-unlock our textures to prevent them from accumulating.
     ReadUnlockTextures();

widget/CompositorWidget.h

@@ -257,6 +257,13 @@ public:
     return mOptions;
   }
 
+  /**
+   * Return true if the window is hidden and should not be composited.
+   */
+  virtual bool IsHidden() const {
+    return false;
+  }
+
   /**
    * This is only used by out-of-process compositors.
    */

widget/windows/WinCompositorWidget.cpp

@@ -327,5 +327,11 @@ WinCompositorWidget::FreeWindowSurface(HDC dc)
     ::ReleaseDC(mWnd, dc);
 }
 
+bool
+WinCompositorWidget::IsHidden() const
+{
+  return ::IsIconic(mWnd);
+}
+
 } // namespace widget
 } // namespace mozilla

widget/windows/WinCompositorWidget.h

@@ -64,6 +64,7 @@ public:
   CompositorWidgetDelegate* AsDelegate() override {
     return this;
   }
+  bool IsHidden() const override;
 
   // CompositorWidgetDelegate overrides.
   void EnterPresentLock() override;