Fix crash in StaticHTMLNativeContent when deallocating WKWebView on iOS9

ios/chrome/browser/ui/static_content/static_html_native_content.mm

Index: ios/chrome/browser/ui/static_content/static_html_native_content.mm
diff --git a/ios/chrome/browser/ui/static_content/static_html_native_content.mm b/ios/chrome/browser/ui/static_content/static_html_native_content.mm
index bfaa5a8905ef033758733bc89b46719e8296ef61..29021b62e8dd30f5570d3d1c3888f2c97f164546 100644
--- a/ios/chrome/browser/ui/static_content/static_html_native_content.mm
+++ b/ios/chrome/browser/ui/static_content/static_html_native_content.mm
@@ -85,13 +85,19 @@
 - (void)setOverscrollActionsController:
     (OverscrollActionsController*)controller {
   _overscrollActionsController.reset([controller retain]);
+  [[self scrollView] setDelegate:controller];
 }
 
 #pragma mark -
 #pragma mark CRWNativeContent implementation
 
-- (void)close {
+- (void)willBeDismissed {
   [_overscrollActionsController invalidate];
+  [[self scrollView] setDelegate:nil];
+}
+
+- (void)close {
+  [self willBeDismissed];

[Eugene But (OOO till 7-30), 2017/01/04 17:52:18]

According to |willBeDismissed| comments this is called when CRWNativeContent
will be removed from superview, which is not the case here. So I don't think it
is fair to call  |willBeDismissed| from |close.|.

 }
 
 - (void)willUpdateSnapshot {