Set CRWWebViewContentView's size before resetting scroll proxy.

ios/web/web_state/ui/crw_wk_web_view_web_controller.mm

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/web/web_state/ui/crw_wk_web_view_web_controller.h"
 
 #import <WebKit/WebKit.h>
 #include <stddef.h>
 
 #include <utility>
@@ skipping 570 matching lines @@
 }
 
 - (void)willLoadCurrentURLInWebView {
   // TODO(stuartmorgan): Get a WKWebView version of the request ID verification
   // code working for debug builds.
 }
 
 - (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];
   BOOL isFormResubmission =
       (holder->navigation_type() == WKNavigationTypeFormResubmitted ||
        holder->navigation_type() == WKNavigationTypeFormSubmitted);
   web::NavigationItemImpl* currentItem =
       [self currentSessionEntry].navigationItemImpl;
   NSData* POSTData = currentItem->GetPostData();
   NSMutableURLRequest* request = [self requestForCurrentNavigationItem];
@@ skipping 1452 matching lines @@
         runJavaScriptTextInputPanelWithPrompt:prompt
                                   defaultText:defaultText
                                    requestURL:requestURL
                             completionHandler:completionHandler];
   } else if (completionHandler) {
     completionHandler(nil);
   }
 }
 
 @end