Bug 1123080 - Use cairo's image backend as canvas fallback on windows. r=Bas

gfx/2d/DrawTargetCairo.cpp

@@ -1522,8 +1522,9 @@ bool
 DrawTargetCairo::InitAlreadyReferenced(cairo_surface_t* aSurface, const IntSize& aSize, SurfaceFormat* aFormat)
 {
   if (cairo_surface_status(aSurface)) {
-    gfxCriticalError() << "Attempt to create DrawTarget for invalid surface. "
-                       << aSize << " Cairo Status: " << cairo_surface_status(aSurface);
+    gfxCriticalError(CriticalLog::DefaultOptions(Factory::ReasonableSurfaceSize(aSize)))
+      << "Attempt to create DrawTarget for invalid surface. "
+      << aSize << " Cairo Status: " << cairo_surface_status(aSurface);
     cairo_surface_destroy(aSurface);
     return false;
   }

gfx/thebes/gfxPlatform.cpp

@@ -1181,7 +1181,12 @@ gfxPlatform::CreateOffscreenCanvasDrawTarget(const IntSize& aSize, SurfaceFormat
     return target.forget();
   }
 
+#ifdef XP_WIN
+  // On Windows, the fallback backend (Cairo) should use its image backend.
+  return Factory::CreateDrawTarget(mFallbackCanvasBackend, aSize, aFormat);
+#else
   return CreateDrawTargetForBackend(mFallbackCanvasBackend, aSize, aFormat);
+#endif
 }
 
 TemporaryRef<DrawTarget>