Move GIF decoder's aggressive purge into ImageDecoder

third_party/WebKit/Source/platform/image-decoders/ImageDecoder.h

Index: third_party/WebKit/Source/platform/image-decoders/ImageDecoder.h
diff --git a/third_party/WebKit/Source/platform/image-decoders/ImageDecoder.h b/third_party/WebKit/Source/platform/image-decoders/ImageDecoder.h
index 51c81a37251705429adeecc8aa2a694606ffd686..70fba8b3d6a92be752566883c17bb34568ddfde6 100644
--- a/third_party/WebKit/Source/platform/image-decoders/ImageDecoder.h
+++ b/third_party/WebKit/Source/platform/image-decoders/ImageDecoder.h
@@ -277,7 +277,8 @@ protected:
     ImageDecoder(AlphaOption alphaOption, GammaAndColorProfileOption colorOptions, size_t maxDecodedBytes)
         : m_premultiplyAlpha(alphaOption == AlphaPremultiplied)
         , m_ignoreGammaAndColorProfile(colorOptions == GammaAndColorProfileIgnored)
-        , m_maxDecodedBytes(maxDecodedBytes) { }
+        , m_maxDecodedBytes(maxDecodedBytes)
+        , m_purgeAggressively(false) { }
 
     // Calculates the most recent frame whose image data may be needed in
     // order to decode frame |frameIndex|, based on frame disposal methods
@@ -330,6 +331,13 @@ protected:
     // memory devices.
     const size_t m_maxDecodedBytes;
 
+    // While decoding, we may learn that there are so many animation frames that
+    // we would go beyond our cache budget.
+    // If that happens, m_purgeAggressively is set to true. This signals
+    // future decodes to purge old frames as it goes.
+    void updateAggressivePurging(size_t index);
+    bool m_purgeAggressively;
+
 private:
     enum class SniffResult {
         JPEG,