Bug 930516 - Add a gfxPlatform::ScreenReferenceDrawTarget() static method. r=Bas

gfx/thebes/gfxPlatform.cpp

@@ -393,6 +393,15 @@ gfxPlatform::Init()
         NS_RUNTIMEABORT("Could not initialize mScreenReferenceSurface");
     }
 
+    if (gPlatform->SupportsAzureContent()) {
+        gPlatform->mScreenReferenceDrawTarget =
+            gPlatform->CreateOffscreenContentDrawTarget(IntSize(1, 1),
+                                                        FORMAT_B8G8R8A8);
+      if (!gPlatform->mScreenReferenceDrawTarget) {
+        NS_RUNTIMEABORT("Could not initialize mScreenReferenceDrawTarget");
+      }
+    }
+
     rv = gfxFontCache::Init();
     if (NS_FAILED(rv)) {
         NS_RUNTIMEABORT("Could not initialize gfxFontCache");
@@ -500,6 +509,7 @@ gfxPlatform::Shutdown()
 gfxPlatform::~gfxPlatform()
 {
     mScreenReferenceSurface = nullptr;
+    mScreenReferenceDrawTarget = nullptr;
 
     // The cairo folks think we should only clean up in debug builds,
     // but we're generally in the habit of trying to shut down as

gfx/thebes/gfxPlatform.h

@@ -578,6 +578,7 @@ public:
      * for measuring text etc as if they will be rendered to the screen
      */
     gfxASurface* ScreenReferenceSurface() { return mScreenReferenceSurface; }
+    mozilla::gfx::DrawTarget* ScreenReferenceDrawTarget() { return mScreenReferenceDrawTarget; }
 
     virtual mozilla::gfx::SurfaceFormat Optimal2DFormatForContent(gfxContentType aContent);
 
@@ -710,6 +711,7 @@ private:
     virtual bool SupportsOffMainThreadCompositing() { return true; }
 
     nsRefPtr<gfxASurface> mScreenReferenceSurface;
+    mozilla::RefPtr<mozilla::gfx::DrawTarget> mScreenReferenceDrawTarget;
     nsTArray<uint32_t> mCJKPrefLangs;
     nsCOMPtr<nsIObserver> mSRGBOverrideObserver;
     nsCOMPtr<nsIObserver> mFontPrefsObserver;