Build with Xcode 9, iOS 11 SDK, launch ios_chrome_integration_egtests, and wait. It will never complete, get stuck in ContextMenuTestCase/testContextMenuOpenInNewTabFromTallPage after a failure with ContextMenuTestCase/ContextMenuTestCase.

Failure is:

UI Test Activity: 
Assertion Failure: context_menu_egtest.mm:81: failed: caught "NSInternalInconsistencyException", "Attempting to transfer an animation to an animation state that is not a direct child of the animation's animation state."
(
	0   CoreFoundation                      0x0000000115bd9f6b __exceptionPreprocess + 171
	1   libobjc.A.dylib                     0x000000011afc5121 objc_exception_throw + 48
	2   CoreFoundation                      0x0000000115bdefd2 +[NSException raise:format:arguments:] + 98
	3   Foundation                          0x0000000116a3ec8a -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 193
	4   UIKit                               0x0000000113b669ee -[UIViewAnimationState _transferAnimationToTrackingAnimator:] + 648
	5   UIKit                               0x00000001147d4ea2 __85+[UIViewPropertyAnimator _animationBlockForTrackingAnimation:animator:trackingSetup:]_block_invoke + 103
	6   UIKit                               0x00000001147d6f25 -[UIViewPropertyAnimator _runAnimations] + 222
	7   UIKit                               0x00000001147df002 __49-[UIViewPropertyAnimator startAnimationAsPaused:]_block_invoke_2 + 103
	8   UIKit                               0x00000001147dee3a __49-[UIViewPropertyAnimator startAnimationAsPaused:]_block_invoke + 146
	9   UIKit                               0x00000001147def71 __49-[UIViewPropertyAnimator startAnimationAsPaused:]_block_invoke.1008 + 258
	10  UIKit                               0x00000001147de578 -[UIViewPropertyAnimator _setupAnimationTracking:] + 128
	11  UIKit                               0x00000001147deb05 -[UIViewPropertyAnimator startAnimationAsPaused:] + 1129
	12  UIKit                               0x00000001147d50ce +[UIViewPropertyAnimator _trackAnimationWithAnimator:forLayer:forAnimationKey:trackingSetup:] + 401
	13  UIKit                               0x00000001147d53db +[UIViewPropertyAnimator _trackAdditiveAnimationWithAnimator:nonAdditiveAnimation:withAnimationKey:forKeyPath:forLayer:] + 249
	14  UIKit                               0x0000000113b6606e __67-[_UIViewAdditiveAnimationAction runActionForKey:object:arguments:]_block_invoke.103 + 1255
	15  UIKit                               0x0000000113b658d6 -[_UIViewAdditiveAnimationAction runActionForKey:object:arguments:] + 3186
	16  QuartzCore                          0x0000000118fdd970 _ZN2CA5Layer12set_positionERKNS_4Vec2IdEEb + 284
	17  QuartzCore                          0x0000000118fdda60 -[CALayer setPosition:] + 43
	18  UIKit                               0x0000000113b7f622 -[UIView setCenter:] + 233
	19  EarlGrey                            0x00000001191eccd0 -[UIView(GREYAdditions) greyswizzled_setCenter:] + 448
	20  UIKit                               0x00000001148a0f45 __171-[UIAlertControllerVisualStyleActionSheet animateAlertControllerView:ofAlertController:forPresentation:inContainerView:descendantOfContainerView:duration:completionBlock:]_block_invoke + 41
	21  UIKit                               0x0000000113b96e05 +[UIView(UIViewAnimationWithBlocks) _setupAnimationWithDuration:delay:view:options:factory:animations:start:animationStateGenerator:completion:] + 560
	22  UIKit                               0x0000000113b9717e +[UIView(UIViewAnimationWithBlocks) animateWithDuration:delay:usingSpringWithDamping:initialSpringVelocity:options:animations:completion:] + 183
	23  EarlGrey                            0x00000001191ee03a +[UIView(GREYAdditions) greyswizzled_animateWithDuration:delay:usingSpringWithDamping:initialSpringVelocity:options:animations:completion:] + 170
	24  UIKit                               0x00000001148a0ed9 -[UIAlertControllerVisualStyleActionSheet animateAlertControllerView:ofAlertController:forPresentation:inContainerView:descendantOfContainerView:duration:completionBlock:] + 888
	25  UIKit                               0x00000001141350ab -[_UIAlertControllerAnimatedTransitioning _animateTransition:completionBlock:] + 646
	26  UIKit                               0x000000011413491a -[_UIAlertControllerAnimatedTransitioning animateTransition:] + 569
	27  UIKit                               0x0000000113c40845 __56-[UIPresentationController runTransitionForCurrentState]_block_invoke + 3003
	28  UIKit                               0x0000000113ae46cc _runAfterCACommitDeferredBlocks + 318
	29  UIKit                               0x0000000113ad2cef _cleanUpAfterCAFlushAndRunDeferredBlocks + 280
	30  UIKit                               0x0000000113b03091 _afterCACommitHandler + 137
	31  CoreFoundation                      0x0000000115b7d507 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 23
	32  CoreFoundation                      0x0000000115b7d45e __CFRunLoopDoObservers + 430
	33  CoreFoundation                      0x0000000115b618f4 __CFRunLoopRun + 1332
	34  CoreFoundation                      0x0000000115b61149 CFRunLoopRunSpecific + 409
	35  EarlGrey                            0x00000001192360df -[GREYRunLoopSpinner grey_drainRunLoopInActiveModeAndCheckCondition:forTime:] + 687
	36  EarlGrey                            0x0000000119235a90 -[GREYRunLoopSpinner spinWithStopConditionBlock:] + 1008
	37  EarlGrey                            0x000000011921bd5f -[GREYTouchInjector waitUntilAllTouchesAreDeliveredUsingInjector] + 719
	38  EarlGrey                            0x000000011921b0d0 -[GREYSyntheticEvents grey_endTouchesAtPoints:timeElapsedSinceLastTouchDelivery:] + 176
	39  EarlGrey                            0x000000011921a15e +[GREYSyntheticEvents touchAlongMultiplePaths:relativeToWindow:forDuration:expendable:] + 1454
	40  EarlGrey                            0x0000000119219b5b +[GREYSyntheticEvents touchAlongPath:relativeToWindow:forDuration:expendable:] + 219
	41  EarlGrey                            0x00000001191dbb65 +[GREYTapper longPressOnElement:location:duration:error:] + 837
	42  EarlGrey                            0x00000001191dac77 -[GREYTapAction perform:error:] + 1527
	43  EarlGrey                            0x000000011920d18c __46-[GREYElementInteraction performAction:error:]_block_invoke + 1084
	44  EarlGrey                            0x000000011923a354 __59-[GREYUIThreadExecutor executeSyncWithTimeout:block:error:]_block_invoke + 68
	45  EarlGrey                            0x0000000119236f01 __54-[GREYRunLoopSpinner grey_checkConditionInActiveMode:]_block_invoke + 401
	46  CoreFoundation                      0x0000000115b7d95c __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12
	47  CoreFoundation                      0x0000000115b61feb __CFRunLoopDoBlocks + 203
	48  CoreFoundation                      0x0000000115b617be __CFRunLoopRun + 1022
	49  CoreFoundation                      0x0000000115b61149 CFRunLoopRunSpecific + 409
	50  EarlGrey                            0x0000000119236c5f -[GREYRunLoopSpinner grey_checkConditionInActiveMode:] + 399
	51  EarlGrey                            0x0000000119235a0a -[GREYRunLoopSpinner spinWithStopConditionBlock:] + 874
	52  EarlGrey                            0x0000000119239dd4 -[GREYUIThreadExecutor executeSyncWithTimeout:block:error:] + 1396
	53  EarlGrey                            0x000000011920c3af -[GREYElementInteraction performAction:error:] + 2175
	54  EarlGrey                            0x000000011920baff -[GREYElementInteraction performAction:] + 79
	55  ios_chrome_integration_egtests      0x00000001096e6e7f _ZN12_GLOBAL__N_130LongPressElementAndTapOnButtonEPKcPU22objcproto11GREYMatcher11objc_object + 511
	56  ios_chrome_integration_egtests      0x00000001096e820e -[ContextMenuTestCase testContextMenuOpenInNewTab] + 1934
	57  CoreFoundation                      0x0000000115b5ec3c __invoking___ + 140
	58  CoreFoundation                      0x0000000115b5eb10 -[NSInvocation invoke] + 320
	59  EarlGrey                            0x0000000119202a28 -[GREYTestCaseInvocation invoke] + 104
	60  XCTest                              0x0000000116f9b7dc __24-[XCTestCase invokeTest]_block_invoke_2 + 451
	61  XCTest                              0x0000000116fe2c2c -[XCUITestContext performInScope:] + 187
	62  XCTest                              0x0000000116f9b5f4 -[XCTestCase invokeTest] + 254
	63  EarlGrey                            0x00000001191f25f8 -[XCTestCase(GREYAdditions) grey_invokeTest] + 1256
	64  XCTest                              0x0000000116f9c520 __26-[XCTestCase performTest:]_block_invoke.362 + 42
	65  XCTest                              0x0000000116fe7471 +[XCTContext runInContextForTestCase:block:] + 163
	66  XCTest                              0x0000000116f9bebc -[XCTestCase performTest:] + 608
	67  XCTest                              0x0000000116f98492 __27-[XCTestSuite performTest:]_block_invoke + 295
	68  XCTest                              0x0000000116f98089 -[XCTestSuite _performProtectedSectionForTest:testSection:] + 26
	69  XCTest                              0x0000000116f9826d -[XCTestSuite performTest:] + 214
	70  XCTest                              0x0000000116f98492 __27-[XCTestSuite performTest:]_block_invoke + 295
	71  XCTest                              0x0000000116f98089 -[XCTestSuite _performProtectedSectionForTest:testSection:] + 26
	72  XCTest                              0x0000000116f9826d -[XCTestSuite performTest:] + 214
	73  XCTest                              0x0000000116f98492 __27-[XCTestSuite performTest:]_block_invoke + 295
	74  XCTest                              0x0000000116f98089 -[XCTestSuite _performProtectedSectionForTest:testSection:] + 26
	75  XCTest                              0x0000000116f9826d -[XCTestSuite performTest:] + 214
	76  XCTest                              0x0000000116fee665 __44-[XCTTestRunSession runTestsAndReturnError:]_block_invoke + 40
	77  XCTest                              0x0000000116faac95 -[XCTestObservationCenter _observeTestExecutionForBlock:] + 480
	78  XCTest                              0x0000000116fee504 -[XCTTestRunSession runTestsAndReturnError:] + 281
	79  XCTest                              0x0000000116f87e43 -[XCTestDriver runTestsAndReturnError:] + 254
	80  XCTest                              0x0000000116fe66f6 _XCTestMain + 616
	81  CoreFoundation                      0x0000000115b7d95c __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12
	82  CoreFoundation                      0x0000000115b61feb __CFRunLoopDoBlocks + 203
	83  CoreFoundation                      0x0000000115b617e4 __CFRunLoopRun + 1060
	84  CoreFoundation                      0x0000000115b61149 CFRunLoopRunSpecific + 409
	85  GraphicsServices                    0x000000011c5089d7 GSEventRunModal + 62
	86  UIKit                               0x0000000113ad891d UIApplicationMain + 159
	87  ios_chrome_integration_egtests      0x000000010815ebdb main + 1051
	88  libdyld.dylib                       0x000000011d031b65 start + 1
)

Mike, can you triage? Is this a failure of EarlGrey related to animation or an issue with Xcode 9/iOS 11 SDK and our animations?