[ios] Fix iOS 10 tab grid animation bug

A bug in WKWebView causes video playback to get gummed up for all future
playbacks even on new WebStates until the app is killed.
This fix runs the simple reduced motion animator for iOS 10 so users
are able to playback video.

Bug: 891851
Change-Id: I22e84f5a7e3b7aa453ba8fe4632ddc12619d86a7
Reviewed-on: https://chromium-review.googlesource.com/c/1330028Reviewed-by: edchin <edchin@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: edchin <edchin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607248}

ios/chrome/browser/ui/tab_grid/tab_grid_transition_handler.mm

@@ -23,32 +23,28 @@
 animationControllerForPresentedController:(UIViewController*)presented
                      presentingController:(UIViewController*)presenting
                          sourceController:(UIViewController*)source {
-  id<UIViewControllerAnimatedTransitioning> animator;
-  if (UIAccessibilityIsReduceMotionEnabled() ||
-      !self.provider.selectedCellVisible) {
-    ReducedMotionAnimator* simpleAnimator =
-        [[ReducedMotionAnimator alloc] init];
-    simpleAnimator.presenting = YES;
-    animator = simpleAnimator;
-  } else {
-    animator =
-        [[GridToVisibleTabAnimator alloc] initWithStateProvider:self.provider];
+  if (@available(iOS 11, *)) {
+    if (!UIAccessibilityIsReduceMotionEnabled() &&
+        self.provider.selectedCellVisible) {
+      return [[GridToVisibleTabAnimator alloc]
+          initWithStateProvider:self.provider];
+    }
   }
-  return animator;
+  ReducedMotionAnimator* simpleAnimator = [[ReducedMotionAnimator alloc] init];
+  simpleAnimator.presenting = YES;
+  return simpleAnimator;
 }
 
 - (id<UIViewControllerAnimatedTransitioning>)
 animationControllerForDismissedController:(UIViewController*)dismissed {
-  id<UIViewControllerAnimatedTransitioning> animator;
-  if (UIAccessibilityIsReduceMotionEnabled()) {
-    ReducedMotionAnimator* simpleAnimator =
-        [[ReducedMotionAnimator alloc] init];
-    simpleAnimator.presenting = NO;
-    animator = simpleAnimator;
-  } else {
-    animator = [[TabToGridAnimator alloc] initWithStateProvider:self.provider];
+  if (@available(iOS 11, *)) {
+    if (!UIAccessibilityIsReduceMotionEnabled()) {
+      return [[TabToGridAnimator alloc] initWithStateProvider:self.provider];
+    }
   }
-  return animator;
+  ReducedMotionAnimator* simpleAnimator = [[ReducedMotionAnimator alloc] init];
+  simpleAnimator.presenting = NO;
+  return simpleAnimator;
 }
 
 @end