Fix the macOS SDAnimatedImageRep to match Netscape standard of GIF loop count, which should use 1 when there are no loop count information

SDWebImage/Core/SDAnimatedImageRep.h

@@ -11,7 +11,8 @@
 #if SD_MAC
 
 /**
- A subclass of `NSBitmapImageRep` to fix that GIF loop count issue because `NSBitmapImageRep` will reset `NSImageCurrentFrameDuration` by using `kCGImagePropertyGIFDelayTime` but not `kCGImagePropertyGIFUnclampedDelayTime`.
+ A subclass of `NSBitmapImageRep` to fix that GIF duration issue because `NSBitmapImageRep` will reset `NSImageCurrentFrameDuration` by using `kCGImagePropertyGIFDelayTime` but not `kCGImagePropertyGIFUnclampedDelayTime`.
+ This also fix the GIF loop count issue, which will use the Netscape standard (See http://www6.uniovi.es/gifanim/gifabout.htm)  to only place once when the `kCGImagePropertyGIFLoopCount` is nil. This is what modern browser's behavior.
  Built in GIF coder use this instead of `NSBitmapImageRep` for better GIF rendering. If you do not want this, only enable `SDImageIOCoder`, which just call `NSImage` API and actually use `NSBitmapImageRep` for GIF image.
  This also support APNG format using `SDImageAPNGCoder`. Which provide full alpha-channel support and the correct duration match the `kCGImagePropertyAPNGUnclampedDelayTime`.
  */

SDWebImage/Core/SDAnimatedImageRep.m

@@ -50,7 +50,10 @@
         }
         if (CFStringCompare(type, kUTTypeGIF, 0) == kCFCompareEqualTo) {
             // GIF
-            // Do nothing because NSBitmapImageRep support it
+            // Fix the `NSBitmapImageRep` GIF loop count calculation issue
+            // Which will use 0 when there are no loop count information metadata in GIF data
+            NSUInteger loopCount = [SDImageGIFCoder imageLoopCountWithSource:imageSource];
+            [self setProperty:NSImageLoopCount withValue:@(loopCount)];
         } else if (CFStringCompare(type, kUTTypePNG, 0) == kCFCompareEqualTo) {
             // APNG
             // Do initilize about frame count, current frame/duration and loop count

Tests/Tests/SDImageCoderTests.m

@@ -103,12 +103,7 @@
     NSString * testImagePath = [[NSBundle bundleForClass:[self class]] pathForResource:@"TestLoopCount" ofType:@"gif"];
     NSData *testImageData = [NSData dataWithContentsOfFile:testImagePath];
     UIImage *image = [SDImageGIFCoder.sharedCoder decodedImageWithData:testImageData options:nil];
-#if SD_MAC
-    // TODO, macOS's `NSBitmapImageRep` treate this loop count as 0, this need to be fixed in next PR.
-    expect(image.sd_imageLoopCount).equal(0);
-#else
     expect(image.sd_imageLoopCount).equal(1);
-#endif
 }
 
 - (void)test13ThatHEICWorks {