Shrink ASImageNode by .6% and ASNetworkImageNode by 2.2% (#1487)

* Shrink ASImageNode by .6% and ASNetworkImageNode by 2.2%

ASImageNode goes from 1384 to 1376. ASNetworkImageNode goes from 1496 to 1464.

These objects accumulate in the heap, so reducing their size will allow more to accumulate before memory warnings.

Group the `BOOL`s into a struct. Shrink the various stored `enum`s to fit the size of their contents. Move the ivars around so that the smaller `enum` are near eachother and the bitfield struct.

* add comments as requested in garrett's review.

* access ivar directly since already locked as suggested in review.

Source/ASImageNode+AnimatedImage.mm

@@ -110,15 +110,15 @@ - (void)setAnimatedImagePaused:(BOOL)animatedImagePaused
 {
   ASLockScopeSelf();
 
-  _animatedImagePaused = animatedImagePaused;
+  _imageNodeFlags.animatedImagePaused = animatedImagePaused;
 
   [self _locked_setShouldAnimate:!animatedImagePaused];
 }
 
 - (BOOL)animatedImagePaused
 {
   ASLockScopeSelf();
-  return _animatedImagePaused;
+  return _imageNodeFlags.animatedImagePaused;
 }
 
 - (void)setCoverImageCompleted:(UIImage *)coverImage
@@ -235,7 +235,7 @@ - (void)_locked_startAnimating
     return;
   }
 
-  if (_animatedImagePaused) {
+  if (_imageNodeFlags.animatedImagePaused) {
     return;
   }
 

Source/ASImageNode.mm

@@ -147,8 +147,6 @@ @implementation ASImageNode
   ASTextNode *_debugLabelNode;
 
   // Cropping.
-  BOOL _cropEnabled; // Defaults to YES.
-  BOOL _forceUpscaling; //Defaults to NO.
   CGSize _forcedSize; //Defaults to CGSizeZero, indicating no forced size.
   CGRect _cropRect; // Defaults to CGRectMake(0.5, 0.5, 0, 0)
   CGRect _cropDisplayBounds; // Defaults to CGRectNull
@@ -175,8 +173,8 @@ - (instancetype)init
   // initial value. With setting a explicit backgroundColor we can prevent that change.
   self.backgroundColor = [UIColor clearColor];
 
-  _cropEnabled = YES;
-  _forceUpscaling = NO;
+  _imageNodeFlags.cropEnabled = YES;
+  _imageNodeFlags.forceUpscaling = NO;
   _cropRect = CGRectMake(0.5, 0.5, 0, 0);
   _cropDisplayBounds = CGRectNull;
   _placeholderColor = ASDisplayNodeDefaultPlaceholderColor();
@@ -301,8 +299,8 @@ - (NSObject *)drawParametersForAsyncLayer:(_ASDisplayLayer *)layer
   drawParameters->_contentsScale = _contentsScaleForDisplay;
   drawParameters->_backgroundColor = self.backgroundColor;
   drawParameters->_contentMode = self.contentMode;
-  drawParameters->_cropEnabled = _cropEnabled;
-  drawParameters->_forceUpscaling = _forceUpscaling;
+  drawParameters->_cropEnabled = _imageNodeFlags.cropEnabled;
+  drawParameters->_forceUpscaling = _imageNodeFlags.forceUpscaling;
   drawParameters->_forcedSize = _forcedSize;
   drawParameters->_cropRect = _cropRect;
   drawParameters->_cropDisplayBounds = _cropDisplayBounds;
@@ -594,7 +592,7 @@ - (void)clearContents
 - (BOOL)isCropEnabled
 {
   AS::MutexLocker l(__instanceLock__);
-  return _cropEnabled;
+  return _imageNodeFlags.cropEnabled;
 }
 
 - (void)setCropEnabled:(BOOL)cropEnabled
@@ -605,12 +603,12 @@ - (void)setCropEnabled:(BOOL)cropEnabled
 - (void)setCropEnabled:(BOOL)cropEnabled recropImmediately:(BOOL)recropImmediately inBounds:(CGRect)cropBounds
 {
   __instanceLock__.lock();
-  if (_cropEnabled == cropEnabled) {
+  if (_imageNodeFlags.cropEnabled == cropEnabled) {
     __instanceLock__.unlock();
     return;
   }
 
-  _cropEnabled = cropEnabled;
+  _imageNodeFlags.cropEnabled = cropEnabled;
   _cropDisplayBounds = cropBounds;
 
   UIImage *image = _image;
@@ -660,13 +658,13 @@ - (void)setCropRect:(CGRect)cropRect
 - (BOOL)forceUpscaling
 {
   AS::MutexLocker l(__instanceLock__);
-  return _forceUpscaling;
+  return _imageNodeFlags.forceUpscaling;
 }
 
 - (void)setForceUpscaling:(BOOL)forceUpscaling
 {
   AS::MutexLocker l(__instanceLock__);
-  _forceUpscaling = forceUpscaling;
+  _imageNodeFlags.forceUpscaling = forceUpscaling;
 }
 
 - (CGSize)forcedSize