Remove invalid pinch-zoom assert in top_controls_manager

cc/input/top_controls_manager.cc

Index: cc/input/top_controls_manager.cc
diff --git a/cc/input/top_controls_manager.cc b/cc/input/top_controls_manager.cc
index 44ed92049c892a58f8b4dfd778b3303266dd38fe..c20d310d5b92c5af8129bf20bbadc2d41bb48514 100644
--- a/cc/input/top_controls_manager.cc
+++ b/cc/input/top_controls_manager.cc
@@ -95,7 +95,9 @@ void TopControlsManager::UpdateTopControlsState(TopControlsState constraints,
 }
 
 void TopControlsManager::ScrollBegin() {
-  DCHECK(!pinch_gesture_active_);
+  if (pinch_gesture_active_)
+    return;
+
   ResetAnimations();
   ResetBaseline();
 }
@@ -132,7 +134,9 @@ gfx::Vector2dF TopControlsManager::ScrollBy(
 }
 
 void TopControlsManager::ScrollEnd() {
-  DCHECK(!pinch_gesture_active_);
+  if (pinch_gesture_active_)
+    return;
+
   StartAnimationIfNecessary();
 }