Add a static method to WebPDecoder to decode WebP

components/image_fetcher/ios/ios_image_data_fetcher_wrapper.mm

Index: components/image_fetcher/ios/ios_image_data_fetcher_wrapper.mm
diff --git a/components/image_fetcher/ios/ios_image_data_fetcher_wrapper.mm b/components/image_fetcher/ios/ios_image_data_fetcher_wrapper.mm
index 247a8475a29594cd9446e6ec4766bdafdf8f1500..233731ebe0372517404917998ad808fa23f3046a 100644
--- a/components/image_fetcher/ios/ios_image_data_fetcher_wrapper.mm
+++ b/components/image_fetcher/ios/ios_image_data_fetcher_wrapper.mm
@@ -5,7 +5,6 @@
 #import "components/image_fetcher/ios/ios_image_data_fetcher_wrapper.h"
 
 #import "base/mac/bind_objc_block.h"
-#import "base/mac/scoped_nsobject.h"
 #include "base/memory/ptr_util.h"
 #include "base/task_runner.h"
 #include "base/task_runner_util.h"
@@ -19,56 +18,6 @@
 #error "This file requires ARC support."
 #endif
 
-#pragma mark - WebpDecoderDelegate
-
-namespace {
-
-// TODO(crbug.com/687921): Refactor this.
-class WebpDecoderDelegate : public webp_transcode::WebpDecoder::Delegate {
- public:
-  WebpDecoderDelegate() = default;
-
-  NSData* data() const { return decoded_image_; }
-
-  // WebpDecoder::Delegate methods
-  void OnFinishedDecoding(bool success) override {
-    if (!success)
-      decoded_image_ = nil;
-  }
-  void SetImageFeatures(
-      size_t total_size,
-      webp_transcode::WebpDecoder::DecodedImageFormat format) override {
-    decoded_image_ = [[NSMutableData alloc] initWithCapacity:total_size];
-  }
-  void OnDataDecoded(NSData* data) override {
-    DCHECK(decoded_image_);
-    [decoded_image_ appendData:data];
-  }
-
- private:
-  ~WebpDecoderDelegate() override = default;
-  NSMutableData* decoded_image_;
-
-  DISALLOW_COPY_AND_ASSIGN(WebpDecoderDelegate);
-};
-
-// Content-type header for WebP images.
-const char kWEBPFirstMagicPattern[] = "RIFF";
-const char kWEBPSecondMagicPattern[] = "WEBP";
-
-// Returns a NSData object containing the decoded image.
-// Returns nil in case of failure.
-NSData* DecodeWebpImage(NSData* webp_image) {
-  scoped_refptr<WebpDecoderDelegate> delegate(new WebpDecoderDelegate);
-  scoped_refptr<webp_transcode::WebpDecoder> decoder(
-      new webp_transcode::WebpDecoder(delegate.get()));
-  decoder->OnDataReceived(webp_image);
-  DLOG_IF(ERROR, !delegate->data()) << "WebP image decoding failed.";
-  return delegate->data();
-}
-
-}  // namespace
-
 #pragma mark - IOSImageDataFetcherWrapper
 
 namespace image_fetcher {
@@ -118,21 +67,21 @@ IOSImageDataFetcherWrapper::CallbackForImageDataFetcher(
     NSData* data =
         [NSData dataWithBytes:image_data.data() length:image_data.size()];
 
-    if (data.length < 12 ||
-        image_data.compare(0, 4, kWEBPFirstMagicPattern) != 0 ||
-        image_data.compare(8, 4, kWEBPSecondMagicPattern) != 0) {
+    if (!webp_transcode::WebpDecoder::IsWebpImage(image_data)) {
       callback(data, metadata);
       return;
     }
 
+    // The image is a webp image.
     RequestMetadata webp_metadata = metadata;
 
-    // The image is a webp image.
-    base::PostTaskAndReplyWithResult(task_runner.get(), FROM_HERE,
-                                     base::Bind(&DecodeWebpImage, data),
-                                     base::BindBlockArc(^(NSData* data) {
-                                       callback(data, webp_metadata);
-                                     }));
+    base::PostTaskAndReplyWithResult(
+        task_runner.get(), FROM_HERE, base::BindBlockArc(^NSData*() {
+          return webp_transcode::WebpDecoder::DecodeWebpImage(data);
+        }),
+        base::BindBlockArc(^(NSData* decodedData) {
+          callback(decodedData, webp_metadata);
+        }));
   });
 }