Set CRWWebViewContentView's size before resetting scroll proxy.

ios/web/web_state/ui/crw_wk_web_view_web_controller.mm

Index: ios/web/web_state/ui/crw_wk_web_view_web_controller.mm
diff --git a/ios/web/web_state/ui/crw_wk_web_view_web_controller.mm b/ios/web/web_state/ui/crw_wk_web_view_web_controller.mm
index de29b293c2da896d3da9b639632678324333a1ba..7ecb0d445d9e3d2cca7dcae5b7ea203ccb53bc21 100644
--- a/ios/web/web_state/ui/crw_wk_web_view_web_controller.mm
+++ b/ios/web/web_state/ui/crw_wk_web_view_web_controller.mm
@@ -588,6 +588,8 @@ WKWebViewErrorSource WKWebViewErrorSourceFromError(NSError* error) {
 - (void)loadRequestForCurrentNavigationItem {
   DCHECK(self.webView && !self.nativeController);
   DCHECK([self currentSessionEntry]);
+  DCHECK(CGRectGetWidth(self.webView.frame) > 0.0);

[shreyasv1, 2016/02/09 22:58:18]

DCHECK_GE?

[kkhorimoto, 2016/02/10 00:08:36]

Done.

+  DCHECK(CGRectGetHeight(self.webView.frame) > 0.0);

[stuartmorgan, 2016/02/09 23:00:51]

CGRectIsNull?

Also, a brief comment here explaining why the check, maybe referencing the bug,
would be helpful, so that if someone hits the DCHECK in a year they'll
understand why it's there and not just remove it.

[kkhorimoto, 2016/02/10 00:08:36]

CGRectIsNull specifically checks against {{Inf, Inf}, {0, 0}}, so it can't be
used here.  I also checked whether CGRectIsEmpty would work, but it returns NO
if both size dimensions are negative, so I just used DCHECK_GT as Shreyas
suggested.  I've also added a comment.

 
   web::WKBackForwardListItemHolder* holder =
       [self currentBackForwardListItemHolder];