Add update image memory cost method

SDWebImage/FLAnimatedImage/FLAnimatedImageView+WebCache.m

@@ -175,13 +175,7 @@ static inline FLAnimatedImage * SDWebImageCreateFLAnimatedImage(FLAnimatedImageV
                                            image.sd_FLAnimatedImage = animatedImage;
                                            image.sd_memoryCost = SDWebImageCalculateFLAnimatedImageMemoryCost(animatedImage);
                                            NSString *key = [[SDWebImageManager sharedManager] cacheKeyForURL:url];
-                                           UIImage *cachedImage = [[SDImageCache sharedImageCache] imageFromMemoryCacheForKey:key];
-                                           // If image can be find in memory cache, we update the cost value of cost.
-                                           if (cachedImage) {
-                                               [[SDImageCache sharedImageCache] removeImageForKey:key fromDisk:NO withCompletion:^{
-                                                   [[SDImageCache sharedImageCache] storeImage:image forKey:key toDisk:NO completion:nil];
-                                               }];
-                                           }
+                                           [[SDImageCache sharedImageCache] updateImageMemoryCostWithKey:key];
                                        }
                                        sstrongSelf.image = animatedImage.posterImage;
                                        sstrongSelf.animatedImage = animatedImage;

SDWebImage/SDImageCache.h

@@ -160,6 +160,17 @@ typedef void(^SDWebImageCalculateSizeBlock)(NSUInteger fileCount, NSUInteger tot
  */
 - (void)storeImageDataToDisk:(nullable NSData *)imageData forKey:(nullable NSString *)key;
 
+#pragma mark - Update Ops
+
+/**
+ * Update image memory cost if image already be stored in memory.
+ *
+ *
+ * @param key        The unique image cache key, usually it's image absolute URL
+ * @note After image be stored in memory cache, if image's memory size changes, such as set a large memory associated object to it, or subclass `UIImage` which has its own large memory properties, you can use this to update memory cost which can make memory cache handle `maxMemoryCost` correctly
+ */
+- (void)updateImageMemoryCostWithKey:(nullable NSString *)key;
+
 #pragma mark - Query and Retrieve Ops
 
 /**

SDWebImage/SDImageCache.m

@@ -357,6 +357,18 @@
     }
 }
 
+#pragma mark - Update Ops
+
+- (void)updateImageMemoryCostWithKey:(NSString *)key {
+    UIImage *cachedImage = [self imageFromMemoryCacheForKey:key];
+    // If image can be find in memory cache, we update the cost value of cost.
+    if (cachedImage) {
+        [self removeImageForKey:key fromDisk:NO withCompletion:^{
+            [self storeImage:cachedImage forKey:key toDisk:NO completion:nil];
+        }];
+    }
+}
+
 #pragma mark - Query and Retrieve Ops
 
 - (void)diskImageExistsWithKey:(nullable NSString *)key completion:(nullable SDWebImageCheckCacheCompletionBlock)completionBlock {