Pass implementation object to supplemental classes by reference

Source/core/rendering/RenderFullScreen.cpp

Index: Source/core/rendering/RenderFullScreen.cpp
diff --git a/Source/core/rendering/RenderFullScreen.cpp b/Source/core/rendering/RenderFullScreen.cpp
index 664bc0244dd79477e63a5af4046dd5ac99180ed3..34b1375570bf45a9ef0d53dbb3564fe79e77c3b1 100644
--- a/Source/core/rendering/RenderFullScreen.cpp
+++ b/Source/core/rendering/RenderFullScreen.cpp
@@ -76,9 +76,9 @@ void RenderFullScreen::willBeDestroyed()
 
     // RenderObjects are unretained, so notify the document (which holds a pointer to a RenderFullScreen)
     // if it's RenderFullScreen is destroyed.
-    FullscreenElementStack* controller = FullscreenElementStack::from(&document());
-    if (controller->fullScreenRenderer() == this)
-        controller->fullScreenRendererDestroyed();
+    FullscreenElementStack& controller = FullscreenElementStack::from(document());
+    if (controller.fullScreenRenderer() == this)
+        controller.fullScreenRendererDestroyed();
 
     RenderFlexibleBox::willBeDestroyed();
 }
@@ -140,7 +140,8 @@ RenderObject* RenderFullScreen::wrapRenderer(RenderObject* object, RenderObject*
         fullscreenRenderer->setNeedsLayoutAndPrefWidthsRecalc();
     }
 
-    FullscreenElementStack::from(document)->setFullScreenRenderer(fullscreenRenderer);
+    ASSERT(document);
+    FullscreenElementStack::from(*document).setFullScreenRenderer(fullscreenRenderer);
     return fullscreenRenderer;
 }
 
@@ -162,7 +163,7 @@ void RenderFullScreen::unwrapRenderer()
     if (placeholder())
         placeholder()->remove();
     remove();
-    FullscreenElementStack::from(&document())->setFullScreenRenderer(0);
+    FullscreenElementStack::from(document()).setFullScreenRenderer(0);
 }
 
 void RenderFullScreen::setPlaceholder(RenderBlock* placeholder)