Bug 769021; fix a memory leak with mask sharing. r=khuey

layout/base/FrameLayerBuilder.cpp

@@ -3296,28 +3296,24 @@ ContainerState::SetupMaskLayer(Layer *aLayer, const FrameLayerBuilder::Clip& aCl
   gfxMatrix imageTransform = maskTransform;
   imageTransform.Scale(mParameters.mXScale, mParameters.mYScale);
 
+  nsAutoPtr<MaskLayerImageCache::MaskLayerImageKey> newKey(
+    new MaskLayerImageCache::MaskLayerImageKey(aLayer->Manager()->GetBackendType()));
+
   // copy and transform the rounded rects
-  nsTArray<MaskLayerImageCache::PixelRoundedRect> roundedRects;
   for (uint32_t i = 0; i < newData.mRoundedClipRects.Length(); ++i) {
-    roundedRects.AppendElement(
+    newKey->mRoundedClipRects.AppendElement(
       MaskLayerImageCache::PixelRoundedRect(newData.mRoundedClipRects[i],
                                             mContainerFrame->PresContext()));
-    roundedRects[i].ScaleAndTranslate(imageTransform);
+    newKey->mRoundedClipRects[i].ScaleAndTranslate(imageTransform);
   }
  
-  // check to see if we can reuse a mask image
-  const MaskLayerImageCache::MaskLayerImageKey* key =
-    new MaskLayerImageCache::MaskLayerImageKey(roundedRects, aLayer->Manager()->GetBackendType());
-  const MaskLayerImageCache::MaskLayerImageKey* lookupKey = key;
+  const MaskLayerImageCache::MaskLayerImageKey* lookupKey = newKey;
 
+  // check to see if we can reuse a mask image
   nsRefPtr<ImageContainer> container =
     GetMaskLayerImageCache()->FindImageFor(&lookupKey);
 
-  if (container) {
-    // track the returned key for the mask image
-    delete key;
-    key = lookupKey;
-  } else {
+  if (!container) {
     // no existing mask image, so build a new one
     nsRefPtr<gfxASurface> surface =
       aLayer->Manager()->CreateOptimalMaskSurface(surfaceSize);
@@ -3348,7 +3344,7 @@ ContainerState::SetupMaskLayer(Layer *aLayer, const FrameLayerBuilder::Clip& aCl
     static_cast<CairoImage*>(image.get())->SetData(data);
     container->SetCurrentImageInTransaction(image);
 
-    GetMaskLayerImageCache()->PutImage(key, container);
+    GetMaskLayerImageCache()->PutImage(newKey.forget(), container);
   }
 
   maskLayer->SetContainer(container);
@@ -3358,7 +3354,7 @@ ContainerState::SetupMaskLayer(Layer *aLayer, const FrameLayerBuilder::Clip& aCl
   userData->mScaleX = newData.mScaleX;
   userData->mScaleY = newData.mScaleY;
   userData->mRoundedClipRects.SwapElements(newData.mRoundedClipRects);
-  userData->mImageKey = key;
+  userData->mImageKey = lookupKey;
 
   aLayer->SetMaskLayer(maskLayer);
   SetClipCount(thebesData, aRoundedRectClipCount);

layout/base/MaskLayerImageCache.cpp

@@ -12,10 +12,13 @@ namespace mozilla {
 
 MaskLayerImageCache::MaskLayerImageCache()
 {
+  MOZ_COUNT_CTOR(MaskLayerImageCache);
   mMaskImageContainers.Init();
 }
 MaskLayerImageCache::~MaskLayerImageCache()
-{}
+{
+  MOZ_COUNT_DTOR(MaskLayerImageCache);
+}
 
 
 /* static */ PLDHashOperator

layout/base/MaskLayerImageCache.h

@@ -50,10 +50,24 @@ public:
               aPresContext->AppUnitsToGfxUnits(aRRect.mRect.width),
               aPresContext->AppUnitsToGfxUnits(aRRect.mRect.height))
     {
+      MOZ_COUNT_CTOR(PixelRoundedRect);
       NS_FOR_CSS_HALF_CORNERS(corner) {
         mRadii[corner] = aPresContext->AppUnitsToGfxUnits(aRRect.mRadii[corner]);
       }
     }
+    PixelRoundedRect(const PixelRoundedRect& aPRR)
+      : mRect(aPRR.mRect)
+    {
+      MOZ_COUNT_CTOR(PixelRoundedRect);
+      NS_FOR_CSS_HALF_CORNERS(corner) {
+        mRadii[corner] = aPRR.mRadii[corner];
+      }
+    }
+
+    ~PixelRoundedRect()
+    {
+      MOZ_COUNT_DTOR(PixelRoundedRect);
+    }
 
     // Applies the scale and translate components of aTransform.
     // It is an error to pass a matrix which does more than just scale
@@ -99,6 +113,9 @@ public:
     gfxRect mRect;
     // Indices into mRadii are the NS_CORNER_* constants in nsStyleConsts.h
     gfxFloat mRadii[8];
+
+  private:
+    PixelRoundedRect() MOZ_DELETE;
   };
 
   /**
@@ -111,14 +128,27 @@ public:
    * pointers to a key object (the +1 being from the hashtable entry), but this
    * invariant may be temporarily broken.
    */
-  class MaskLayerImageKey
+  struct MaskLayerImageKey
   {
-  public:
-    MaskLayerImageKey(const nsTArray<PixelRoundedRect>& aRoundedClipRects, layers::LayersBackend aBackend)
+    MaskLayerImageKey(layers::LayersBackend aBackend)
       : mBackend(aBackend)
       , mLayerCount(0)
-      , mRoundedClipRects(aRoundedClipRects)
-    {}
+      , mRoundedClipRects()
+    {
+      MOZ_COUNT_CTOR(MaskLayerImageKey);
+    }
+    MaskLayerImageKey(const MaskLayerImageKey& aKey)
+      : mBackend(aKey.mBackend)
+      , mLayerCount(aKey.mLayerCount)
+      , mRoundedClipRects(aKey.mRoundedClipRects)
+    {
+      MOZ_COUNT_CTOR(MaskLayerImageKey);
+    }
+
+    ~MaskLayerImageKey()
+    {
+      MOZ_COUNT_DTOR(MaskLayerImageKey);
+    }
 
     void AddRef() const { ++mLayerCount; }
     void Release() const
@@ -172,11 +202,14 @@ protected:
     typedef const MaskLayerImageKey& KeyType;
     typedef const MaskLayerImageKey* KeyTypePointer;
 
-    MaskLayerImageEntry(KeyTypePointer aKey) : mKey(aKey) {}
-    MaskLayerImageEntry(const MaskLayerImageEntry& aOther)
-      : mKey(aOther.mKey.get())
+    MaskLayerImageEntry(KeyTypePointer aKey) : mKey(aKey)
     {
-      NS_ERROR("ALLOW_MEMMOVE == true, should never be called");
+      MOZ_COUNT_CTOR(MaskLayerImageEntry);
+    }
+    MaskLayerImageEntry(const MaskLayerImageEntry& aOther) MOZ_DELETE;
+    ~MaskLayerImageEntry()
+    {
+      MOZ_COUNT_DTOR(MaskLayerImageEntry);
     }
 
     // KeyEquals(): does this entry match this key?