Bug 967473 - Fix layer diagnostics with tiling. r=BenWa

gfx/layers/composite/TiledContentHost.cpp

@@ -205,9 +205,9 @@ TiledContentHost::RenderTile(const TiledTexture& aTile,
                                   textureRect.width / aTextureBounds.width,
                                   textureRect.height / aTextureBounds.height);
     mCompositor->DrawQuad(graphicsRect, aClipRect, aEffectChain, aOpacity, aTransform);
-    mCompositor->DrawDiagnostics(DIAGNOSTIC_CONTENT|DIAGNOSTIC_TILE,
-                                 graphicsRect, aClipRect, aTransform);
   }
+  mCompositor->DrawDiagnostics(DIAGNOSTIC_CONTENT|DIAGNOSTIC_TILE,
+                               aScreenRegion, aClipRect, aTransform);
 
   aTile.mDeprecatedTextureHost->Unlock();
 }