iOS: fix when RootNode shrink its size, it cannot be layout properly

doric-iOS/Pod/Classes/Shader/DoricRootNode.h

@@ -28,6 +28,8 @@
 
 @interface DoricRootNode : DoricStackNode
 
+@property(nonatomic, assign) CGSize mostFrameSize;
+
 - (void)setupRootView:(UIView *)view;
 
 @end

doric-iOS/Pod/Classes/Shader/DoricRootNode.m

@@ -54,13 +54,25 @@ - (void)setY:(CGFloat)y {
 @end
 
 @implementation DoricRootNode
+
+- (instancetype)initWithContext:(DoricContext *)doricContext {
+    if (self = [super initWithContext:doricContext]) {
+        _mostFrameSize = CGSizeZero;
+    }
+    return self;
+}
+
 - (void)setupRootView:(UIView *)view {
     view.doricLayout.layoutType = DoricStack;
     self.view = view;
 }
 
 - (void)requestLayout {
+    if (CGSizeEqualToSize(self.mostFrameSize, CGSizeZero)) {
         [self.view.doricLayout apply];
+    } else {
+        [self.view.doricLayout apply:self.mostFrameSize];
+    }
     [super requestLayout];
 }
 @end