[ARC] Converts parts of ios/web/web_state to ARC.

ios/web/public/web_state/crw_web_view_scroll_view_proxy.h

Index: ios/web/public/web_state/crw_web_view_scroll_view_proxy.h
diff --git a/ios/web/public/web_state/crw_web_view_scroll_view_proxy.h b/ios/web/public/web_state/crw_web_view_scroll_view_proxy.h
index 7b49f89c3d11d8930130c2c3629ab9f1a97e3ace..7ac4ccbba2eb770f4cfaa9ab9251ea5e43097b15 100644
--- a/ios/web/public/web_state/crw_web_view_scroll_view_proxy.h
+++ b/ios/web/public/web_state/crw_web_view_scroll_view_proxy.h
@@ -31,9 +31,10 @@
 @property(nonatomic, readonly) CGRect frame;
 @property(nonatomic, getter=isScrollEnabled) BOOL scrollEnabled;
 @property(nonatomic, assign) BOOL bounces;
-@property(nonatomic, readonly) UIPanGestureRecognizer* panGestureRecognizer;
+@property(weak, nonatomic, readonly)
+    UIPanGestureRecognizer* panGestureRecognizer;
 // Returns the scrollview's gesture recognizers.
-@property(nonatomic, readonly) NSArray* gestureRecognizers;
+@property(weak, nonatomic, readonly) NSArray* gestureRecognizers;
 
 // Calls UIScrollView's implementation of setContentInset: directly. This
 // bypasses a very slow update path in UIWebView.