blink/images: Don't clear decoder frames for metadata decoder.

The metadata decoder is never used for decoding anything other than the
header, so it should never have any pixel data to evict. Its unnecessary
to evict it from BitmapImage.

R=chrishtr@chromium.org

Bug: 899666
Change-Id: I93a5baa48d95e6c94f7081e9c9c02196a584b9b2
Reviewed-on: https://chromium-review.googlesource.com/c/1305973Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Khushal <khushalsagar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604093}

third_party/blink/renderer/platform/graphics/bitmap_image.cc

@@ -85,8 +85,6 @@ bool BitmapImage::CurrentFrameHasSingleSecurityOrigin() const {
 
 void BitmapImage::DestroyDecodedData() {
   cached_frame_ = PaintImage();
-  if (decoder_)
-    decoder_->ClearCacheExceptFrame(kNotFound);
   NotifyMemoryChanged();
 }
 

third_party/blink/renderer/platform/graphics/deferred_image_decoder.cc

@@ -217,11 +217,6 @@ int DeferredImageDecoder::RepetitionCount() const {
                            : repetition_count_;
 }
 
-void DeferredImageDecoder::ClearCacheExceptFrame(size_t clear_except_frame) {
-  if (metadata_decoder_)
-    metadata_decoder_->ClearCacheExceptFrame(clear_except_frame);
-}
-
 bool DeferredImageDecoder::FrameHasAlphaAtIndex(size_t index) const {
   if (metadata_decoder_)
     return metadata_decoder_->FrameHasAlphaAtIndex(index);

third_party/blink/renderer/platform/graphics/deferred_image_decoder.h

@@ -75,7 +75,6 @@ class PLATFORM_EXPORT DeferredImageDecoder final {
   size_t FrameCount();
   bool ImageIsHighBitDepth() const { return image_is_high_bit_depth_; }
   int RepetitionCount() const;
-  void ClearCacheExceptFrame(size_t index);
   bool FrameHasAlphaAtIndex(size_t index) const;
   bool FrameIsReceivedAtIndex(size_t index) const;
   TimeDelta FrameDurationAtIndex(size_t index) const;