Rollback CADisplayLink change causing a crash in an internal client.

Reviewers: ajsecord, randallli, O1 Material components iOS

Reviewed By: randallli, O1 Material components iOS

Tags: #material_components_ios

Differential Revision: http://codereview.cc/D1497

Author: Ian Gordon

components/FlexibleHeader/src/MDCFlexibleHeaderView.m

@@ -488,15 +488,11 @@ - (float)fhv_dragCoefficient {
 - (void)fhv_startDisplayLink {
   [self fhv_stopDisplayLink];
 
-  // CADisplayLink retains its target. Avoid retain loop by using NSInvocation to hold onto self
-  // with a weak reference.
-  SEL selector = @selector(fhv_shiftAccumulatorDisplayLinkDidFire:);
-  NSInvocation *invocation =
-      [NSInvocation invocationWithMethodSignature:[self methodSignatureForSelector:selector]];
-  invocation.target = self;
-  invocation.selector = selector;
+  // NOTE: This may cause a retain cycle.
+  // cl/129917749
   _shiftAccumulatorDisplayLink =
-      [CADisplayLink displayLinkWithTarget:invocation selector:@selector(invoke)];
+      [CADisplayLink displayLinkWithTarget:self
+                                  selector:@selector(fhv_shiftAccumulatorDisplayLinkDidFire:)];
   [_shiftAccumulatorDisplayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];
 }