Image decoding: Remove deprecated image caching code

Source/platform/graphics/ImageDecodingStore.h

Index: Source/platform/graphics/ImageDecodingStore.h
diff --git a/Source/platform/graphics/ImageDecodingStore.h b/Source/platform/graphics/ImageDecodingStore.h
index 48f191ed879c93947c8fdcefc5895c1c1ec5cfc1..cb8de62d92c02b95cb922813069fd1231fb40fe5 100644
--- a/Source/platform/graphics/ImageDecodingStore.h
+++ b/Source/platform/graphics/ImageDecodingStore.h
@@ -29,8 +29,6 @@
 #include "SkSize.h"
 #include "SkTypes.h"
 #include "platform/PlatformExport.h"
-#include "platform/graphics/DiscardablePixelRef.h"
-#include "platform/graphics/ScaledImageFragment.h"
 #include "platform/graphics/skia/SkSizeHash.h"
 #include "platform/image-decoders/ImageDecoder.h"
 
@@ -48,26 +46,10 @@ class SharedBuffer;
 
 // FUNCTION
 //
-// ImageDecodingStore is a class used to manage image cache objects. There are two
-// types of cache objects stored:
-//
-// 1. Image objects
-//    Each image object belongs to one frame decoded and/or resampled from an image
-//    file. The image object can be complete or partial. Complete means the image
-//    is fully decoded and will not mutate in future decoding passes. It can have
-//    multiple concurrent users. A partial image object has only one user.
-//
-// 2. Decoder objects
-//    A decoder object contains an image decoder. This allows decoding to resume
-//    from previous states. There can be one user per one decoder object at any
-//    time.
+// ImageDecodingStore is a class used to manage cached decoder objects.
 //
 // EXTERNAL OBJECTS
 //
-// ScaledImageFragment
-//   A cached image object. Contains the bitmap and information about the bitmap
-//   image.
-//
 // ImageDecoder
 //   A decoder object. It is used to decode raw data into bitmap images.
 //
@@ -76,9 +58,6 @@ class SharedBuffer;
 //   using an ImageDecoder. It contains encoded image data and is used to represent
 //   one image file. It is used to index image and decoder objects in the cache.
 //
-// LazyDecodingPixelRef
-//   A read only user of this cache.
-//
 // THREAD SAFETY
 //
 // All public methods can be used on any thread.
@@ -90,37 +69,13 @@ public:
 
     static ImageDecodingStore* instance();
 
-    // Why do we need this?
-    // ImageDecodingStore is used in two code paths:
-    // 1. Android uses this to cache both images and decoders.
-    // 2. Skia discardable memory path has its own cache. We still want cache
-    //    decoders but not images because Skia will take care of it.
-    // Because of the two use cases we want to just disable image caching.
-    //
-    // FIXME: It is weird to have this behavior. We want to remove image
-    // caching from this class once the transition to Skia discardable memory
-    // is complete.
-    static void setImageCachingEnabled(bool);
-
-    // Access a complete cached image object. A complete cached image object is
-    // indexed by the origin (ImageFrameGenerator), scaled size and frame index
-    // within the image file.
-    // Return true if the cache object is found.
-    // Return false if the cache object cannot be found or it is incomplete.
-    bool lockCache(const ImageFrameGenerator*, const SkISize& scaledSize, size_t index, const ScaledImageFragment**);
-    void unlockCache(const ImageFrameGenerator*, const ScaledImageFragment*);
-    const ScaledImageFragment* insertAndLockCache(const ImageFrameGenerator*, PassOwnPtr<ScaledImageFragment>);
-
     // Access a cached decoder object. A decoder is indexed by origin (ImageFrameGenerator)
     // and scaled size. Return true if the cached object is found.
     bool lockDecoder(const ImageFrameGenerator*, const SkISize& scaledSize, ImageDecoder**);
     void unlockDecoder(const ImageFrameGenerator*, const ImageDecoder*);
-    void insertDecoder(const ImageFrameGenerator*, PassOwnPtr<ImageDecoder>, bool isDiscardable);
+    void insertDecoder(const ImageFrameGenerator*, PassOwnPtr<ImageDecoder>);
     void removeDecoder(const ImageFrameGenerator*, const ImageDecoder*);
 
-    // Locks the cache for safety, but does not attempt to lock the object we're checking for.
-    bool isCached(const ImageFrameGenerator*, const SkISize& scaledSize, size_t index);
-
     // Remove all cache entries indexed by ImageFrameGenerator.
     void removeCacheIndexedByGenerator(const ImageFrameGenerator*);
 
@@ -128,37 +83,25 @@ public:
     void setCacheLimitInBytes(size_t);
     size_t memoryUsageInBytes();
     int cacheEntries();
-    int imageCacheEntries();
     int decoderCacheEntries();
 
 private:
-    // Image cache entry is identified by:
+    // Decoder cache entry is identified by:
     // 1. Pointer to ImageFrameGenerator.
     // 2. Size of the image.
-    // 3. LocalFrame index.
-    // 4. LocalFrame generation. Increments on each progressive decode.
-    //
-    // The use of generation ID is to allow multiple versions of an image frame
-    // be stored in the cache. Each generation comes from a progressive decode.
-    //
-    // Decoder entries are identified by (1) and (2) only.
     typedef std::pair<const ImageFrameGenerator*, SkISize> DecoderCacheKey;
-    typedef std::pair<size_t, size_t> IndexAndGeneration;
-    typedef std::pair<DecoderCacheKey, IndexAndGeneration> ImageCacheKey;
 
     // Base class for all cache entries.
     class CacheEntry : public DoublyLinkedListNode<CacheEntry> {
         friend class WTF::DoublyLinkedListNode<CacheEntry>;
     public:
         enum CacheType {
-            TypeImage,
             TypeDecoder,
         };
 
-        CacheEntry(const ImageFrameGenerator* generator, int useCount, bool isDiscardable)
+        CacheEntry(const ImageFrameGenerator* generator, int useCount)
             : m_generator(generator)
             , m_useCount(useCount)
-            , m_isDiscardable(isDiscardable)
             , m_prev(0)
             , m_next(0)
         {
@@ -173,7 +116,6 @@ private:
         int useCount() const { return m_useCount; }
         void incrementUseCount() { ++m_useCount; }
         void decrementUseCount() { --m_useCount; ASSERT(m_useCount >= 0); }
-        bool isDiscardable() const { return m_isDiscardable; }
 
         // FIXME: getSafeSize() returns size in bytes truncated to a 32-bits integer.
         //        Find a way to get the size in 64-bits.
@@ -183,52 +125,21 @@ private:
     protected:
         const ImageFrameGenerator* m_generator;
         int m_useCount;
-        bool m_isDiscardable;
 
     private:
         CacheEntry* m_prev;
         CacheEntry* m_next;
     };
 
-    class ImageCacheEntry FINAL : public CacheEntry {
-    public:
-        static PassOwnPtr<ImageCacheEntry> createAndUse(const ImageFrameGenerator* generator, PassOwnPtr<ScaledImageFragment> image)
-        {
-            return adoptPtr(new ImageCacheEntry(generator, 1, image));
-        }
-
-        ImageCacheEntry(const ImageFrameGenerator* generator, int count, PassOwnPtr<ScaledImageFragment> image)
-            : CacheEntry(generator, count, DiscardablePixelRef::isDiscardable(image->bitmap().pixelRef()))
-            , m_cachedImage(image)
-        {
-        }
-
-        // FIXME: getSafeSize() returns size in bytes truncated to a 32-bits integer.
-        //        Find a way to get the size in 64-bits.
-        virtual size_t memoryUsageInBytes() const OVERRIDE { return cachedImage()->bitmap().getSafeSize(); }
-        virtual CacheType type() const OVERRIDE { return TypeImage; }
-
-        static ImageCacheKey makeCacheKey(const ImageFrameGenerator* generator, const SkISize& size, size_t index, size_t generation)
-        {
-            return std::make_pair(std::make_pair(generator, size), std::make_pair(index, generation));
-        }
-        ImageCacheKey cacheKey() const { return makeCacheKey(m_generator, m_cachedImage->scaledSize(), m_cachedImage->index(), m_cachedImage->generation()); }
-        const ScaledImageFragment* cachedImage() const { return m_cachedImage.get(); }
-        ScaledImageFragment* cachedImage() { return m_cachedImage.get(); }
-
-    private:
-        OwnPtr<ScaledImageFragment> m_cachedImage;
-    };
-
     class DecoderCacheEntry FINAL : public CacheEntry {
     public:
-        static PassOwnPtr<DecoderCacheEntry> create(const ImageFrameGenerator* generator, PassOwnPtr<ImageDecoder> decoder, bool isDiscardable)
+        static PassOwnPtr<DecoderCacheEntry> create(const ImageFrameGenerator* generator, PassOwnPtr<ImageDecoder> decoder)
         {
-            return adoptPtr(new DecoderCacheEntry(generator, 0, decoder, isDiscardable));
+            return adoptPtr(new DecoderCacheEntry(generator, 0, decoder));
         }
 
-        DecoderCacheEntry(const ImageFrameGenerator* generator, int count, PassOwnPtr<ImageDecoder> decoder, bool isDiscardable)
-            : CacheEntry(generator, count, isDiscardable)
+        DecoderCacheEntry(const ImageFrameGenerator* generator, int count, PassOwnPtr<ImageDecoder> decoder)
+            : CacheEntry(generator, count)
             , m_cachedDecoder(decoder)
             , m_size(SkISize::Make(m_cachedDecoder->decodedSize().width(), m_cachedDecoder->decodedSize().height()))
         {
@@ -258,12 +169,6 @@ private:
     void prune();
 
     // These helper methods are called while m_mutex is locked.
-
-    // Find and lock a cache entry, and return true on success.
-    // Memory of the cache entry can be discarded, in which case it is saved in
-    // deletionList.
-    bool lockCacheEntryInternal(ImageCacheEntry*, const ScaledImageFragment**, Vector<OwnPtr<CacheEntry> >* deletionList);
-
     template<class T, class U, class V> void insertCacheInternal(PassOwnPtr<T> cacheEntry, U* cacheMap, V* identifierMap);
 
     // Helper method to remove a cache entry. Ownership is transferred to
@@ -287,20 +192,10 @@ private:
     // Tail of this list is the most recently used cache entry.
     DoublyLinkedList<CacheEntry> m_orderedCacheList;
 
-    // A lookup table for all image cache objects. Owns all image cache objects.
-    typedef HashMap<ImageCacheKey, OwnPtr<ImageCacheEntry> > ImageCacheMap;
-    ImageCacheMap m_imageCacheMap;
-
     // A lookup table for all decoder cache objects. Owns all decoder cache objects.
     typedef HashMap<DecoderCacheKey, OwnPtr<DecoderCacheEntry> > DecoderCacheMap;
     DecoderCacheMap m_decoderCacheMap;
 
-    // A lookup table to map ImageFrameGenerator to all associated image
-    // cache keys.
-    typedef HashSet<ImageCacheKey> ImageCacheKeySet;
-    typedef HashMap<const ImageFrameGenerator*, ImageCacheKeySet> ImageCacheKeyMap;
-    ImageCacheKeyMap m_imageCacheKeyMap;
-
     // A lookup table to map ImageFrameGenerator to all associated
     // decoder cache keys.
     typedef HashSet<DecoderCacheKey> DecoderCacheKeySet;
@@ -309,16 +204,13 @@ private:
 
     size_t m_heapLimitInBytes;
     size_t m_heapMemoryUsageInBytes;
-    size_t m_discardableMemoryUsageInBytes;
 
     // Protect concurrent access to these members:
     //   m_orderedCacheList
-    //   m_imageCacheMap, m_decoderCacheMap and all CacheEntrys stored in it
-    //   m_imageCacheKeyMap
+    //   m_decoderCacheMap and all CacheEntrys stored in it
     //   m_decoderCacheKeyMap
     //   m_heapLimitInBytes
     //   m_heapMemoryUsageInBytes
-    //   m_discardableMemoryUsageInBytes
     // This mutex also protects calls to underlying skBitmap's
     // lockPixels()/unlockPixels() as they are not threadsafe.
     Mutex m_mutex;