Revert the changes for unused public API, polish comments

SDWebImage/SDImageCache.h

@@ -160,17 +160,6 @@ 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

@@ -359,18 +359,6 @@
     }
 }
 
-#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 {

SDWebImage/UIImage+CacheMemoryCost.h

@@ -11,10 +11,12 @@
 @interface UIImage (CacheMemoryCost)
 
 /**
- * The image memory cost calculation, this property would be used in memory cache of `SDImageCache`.
- * The default value is pixels of `image` or `images`.
- * If you set some associated object to `UIImage`, you can set the custom value to indicate the memory cost.
- * If you set a new value after `UIImage` be cached to memory cache, you need to reinsert into cache with new value cost by yourself.
+ The memory cache cost for specify image used by image cache. The cost function is the pixles count held in memory.
+ If you set some associated object to `UIImage`, you can set the custom value to indicate the memory cost.
+ 
+ For `UIImage`, this method return the single frame pixles count when `image.images` is nil for static image. Retuen full frame pixels count when `image.images` is not nil for animated image.
+ For `NSImage`, this method return the single frame pixels count because `NSImage` does not store all frames in memory.
+ @note Note that because of the limitations of categories this property can get out of sync if you create another instance with CGImage or other methods.
  */
 @property (assign, nonatomic) NSUInteger sd_memoryCost;
 

Tests/SDWebImage Tests.xcodeproj/project.pbxproj

@@ -159,7 +159,6 @@
 				DA248D50195472AA00390AB0 /* Frameworks */,
 				DA248D51195472AA00390AB0 /* Resources */,
 				C86216497B5A0BA9501E2C07 /* [CP] Embed Pods Frameworks */,
-				85E5D3885A03BFC23B050908 /* [CP] Copy Pods Resources */,
 			);
 			buildRules = (
 			);
@@ -232,21 +231,6 @@
 			shellScript = "diff \"${PODS_PODFILE_DIR_PATH}/Podfile.lock\" \"${PODS_ROOT}/Manifest.lock\" > /dev/null\nif [ $? != 0 ] ; then\n    # print error to STDERR\n    echo \"error: The sandbox is not in sync with the Podfile.lock. Run 'pod install' or update your CocoaPods installation.\" >&2\n    exit 1\nfi\n# This output is used by Xcode 'outputs' to avoid re-running this script phase.\necho \"SUCCESS\" > \"${SCRIPT_OUTPUT_FILE_0}\"\n";
 			showEnvVarsInLog = 0;
 		};
-		85E5D3885A03BFC23B050908 /* [CP] Copy Pods Resources */ = {
-			isa = PBXShellScriptBuildPhase;
-			buildActionMask = 2147483647;
-			files = (
-			);
-			inputPaths = (
-			);
-			name = "[CP] Copy Pods Resources";
-			outputPaths = (
-			);
-			runOnlyForDeploymentPostprocessing = 0;
-			shellPath = /bin/sh;
-			shellScript = "\"${SRCROOT}/Pods/Target Support Files/Pods-Tests/Pods-Tests-resources.sh\"\n";
-			showEnvVarsInLog = 0;
-		};
 		C86216497B5A0BA9501E2C07 /* [CP] Embed Pods Frameworks */ = {
 			isa = PBXShellScriptBuildPhase;
 			buildActionMask = 2147483647;