Bug 899881 - Don't allow frames to have a null style context. r=dbaron

layout/generic/nsFrame.cpp

@@ -394,8 +394,7 @@ nsFrame::~nsFrame()
   MOZ_COUNT_DTOR(nsFrame);
 
   NS_IF_RELEASE(mContent);
-  if (mStyleContext)
+  mStyleContext->Release();
-    mStyleContext->Release();
 }
 
 NS_IMPL_FRAMEARENA_HELPERS(nsFrame)

layout/generic/nsIFrame.h

@@ -751,12 +751,9 @@ public:
     if (aContext != mStyleContext) {
       nsStyleContext* oldStyleContext = mStyleContext;
       mStyleContext = aContext;
-      if (aContext) {
+      aContext->AddRef();
-        aContext->AddRef();
+      DidSetStyleContext(oldStyleContext);
-        DidSetStyleContext(oldStyleContext);
+      oldStyleContext->Release();
-      }
-      if (oldStyleContext)
-        oldStyleContext->Release();
     }
   }
 
@@ -769,12 +766,9 @@ public:
   void SetStyleContextWithoutNotification(nsStyleContext* aContext)
   {
     if (aContext != mStyleContext) {
-      if (mStyleContext)
+      mStyleContext->Release();
-        mStyleContext->Release();
       mStyleContext = aContext;
-      if (aContext) {
+      aContext->AddRef();
-        aContext->AddRef();
-      }
     }
   }