Set CRWWebViewContentView's size before resetting scroll proxy.

ios/web/web_state/ui/crw_web_view_content_view.mm

 // Copyright 2015 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/public/web_state/ui/crw_web_view_content_view.h"
 
 #import <WebKit/WebKit.h>
 
 #include "base/logging.h"
 #include "base/mac/scoped_nsobject.h"
@@ skipping 61 matching lines @@
 - (void)didMoveToSuperview {
   [super didMoveToSuperview];
   if (self.superview) {
     self.autoresizingMask =
         UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
     [self addSubview:_webView];
     self.backgroundColor = [UIColor colorWithRed:kBackgroundRGBComponents[0]
                                            green:kBackgroundRGBComponents[1]
                                             blue:kBackgroundRGBComponents[2]
                                            alpha:1.0];
-    // The frame needs to be set immediately after the web view is added
-    // as a subview. The change in the frame triggers drawing operations and
-    // if not done after it's added as a subview, the web view exhibits
-    // strange behavior where clicks from certain web sites are not triggered.
-    // The actual value of the frame doesn't matter as long as it's not
-    // CGRectZero.  The CRWWebViewContentView's frame will be reset to a correct
-    // value in a subsequent layout pass.
-    // TODO(crbug.com/577793): This is an undocumented and not-well-understood
-    // workaround for this issue.
-    const CGRect kDummyRect = CGRectMake(10, 20, 30, 50);
-    self.frame = kDummyRect;

[stuartmorgan, 2016/02/09 21:27:50]

Would it be worth adding a DCHECK here that the frame isn't zero/invalid, with a
brief comment explaining why, just to be sure we never regress this on accident?

[shreyasv1, 2016/02/09 21:58:29]

The fact that it's non zero is a coincidence from the embedder's side.
When a UIView is instantiated it's bounds is CGRectZero. 
Whenever a WebController is alloc, inited the CRWWebControllerContainerView has
a bounds of CGRectZero.

Given that, adding a DCHECK is the wrong thing here.

[stuartmorgan, 2016/02/09 22:15:19]

If having it be non-zero avoids critical bugs, then it's not a coincidence, it's
something embedders need to do.

[kkhorimoto, 2016/02/09 22:17:11]

I think it'd be better to add a DCHECK in
|-loadRequestForCurrentNavigationItem|, since all that really matters is that it
has a valid size before attempting to load/render anything.

   }
 }
 
 - (BOOL)becomeFirstResponder {
   return [_webView becomeFirstResponder];
 }
 
 #pragma mark Accessors
 
 - (UIScrollView*)scrollView {
@@ skipping 40 matching lines @@
 
 - (void)updateWebViewFrame {
   CGRect webViewFrame = self.bounds;
   webViewFrame.size.height -= _topContentPadding;
   webViewFrame.origin.y += _topContentPadding;
 
   self.webView.frame = webViewFrame;
 }
 
 @end