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 180ec29bba7c2d0dc0142d04eaaf63ba5e5f78bb..ced7fa20be5d37b52973e14a9092060ed589e8f5 100644
--- a/third_party/WebKit/Source/platform/image-decoders/ImageDecoder.h
+++ b/third_party/WebKit/Source/platform/image-decoders/ImageDecoder.h
@@ -279,7 +279,8 @@ class PLATFORM_EXPORT ImageDecoder {
       : 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
@@ -332,6 +333,13 @@ class PLATFORM_EXPORT ImageDecoder {
   // 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, PNG, GIF, WEBP, ICO, BMP, Invalid };