Implement CWVWebView.scrollView.

ios/web_view/public/cwv_scroll_view.h

Index: ios/web_view/public/cwv_scroll_view.h
diff --git a/ios/web_view/public/cwv_scroll_view.h b/ios/web_view/public/cwv_scroll_view.h
new file mode 100644
index 0000000000000000000000000000000000000000..72fda91e28e1475fe69bf8a9707ed77e7eceb0e8
--- /dev/null
+++ b/ios/web_view/public/cwv_scroll_view.h
@@ -0,0 +1,42 @@
+// Copyright 2017 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.
+
+#ifndef IOS_WEB_VIEW_PUBLIC_CWV_SCROLL_VIEW_H_
+#define IOS_WEB_VIEW_PUBLIC_CWV_SCROLL_VIEW_H_
+
+#import <ChromeWebView/cwv_export.h>
+#import <CoreGraphics/CoreGraphics.h>
+#import <Foundation/Foundation.h>
+#import <UIKit/UIKit.h>
+
+@protocol CWVScrollViewDelegate;
+
+// Scroll view inside the web view. Has subset of methods of
+// UIScrollView. This is not a subclass of UIScrollView because
+// we don't want to expose the raw scroll view.

[Eugene But (OOO till 7-30), 2017/04/26 19:11:31]

Please avoid using "we" in the comments (go/avoidwe)

[Hiroshi Ichikawa, 2017/04/27 02:30:11]

Done.

+//
+// See the document of UIScrollView for the document of each
+// method.
+//
+// TODO: Add nullability annotations.
+CWV_EXPORT
+@interface CWVScrollView : NSObject
+
+@property(nonatomic, readonly) CGRect frame;
+@property(nonatomic, readonly) CGRect bounds;
+@property(nonatomic) CGPoint contentOffset;
+@property(nonatomic, readonly) CGSize contentSize;
+@property(nonatomic, weak) id<CWVScrollViewDelegate> delegate;
+@property(nonatomic, readonly, getter=isDragging) BOOL dragging;
+- (void)addGestureRecognizer:(UIGestureRecognizer*)gestureRecognizer;
+
+// Be careful when using this property. There's a bug with the
+// underlying WKWebView where the web view does not respect
+// contentInsets properly. See:
+// https://chromereviews.googleplex.com/323287014/

[Eugene But (OOO till 7-30), 2017/04/26 19:11:31]

Please link rdar://23584409 instead of internal google CL

[Hiroshi Ichikawa, 2017/04/27 02:30:11]

Looks like the issue is not visible at Open Radar?
https://openradar.appspot.com/23584409
In that case, I believe the code review URL is more useful because people cannot
get more information from the rdar URL. What do you think? I put both of the
code review URL and the rdar URL for now.

[Eugene But (OOO till 7-30), 2017/04/27 12:25:23]

In Chromium we do not use links to internal google services. rdar://23584409 is
also internal, and if you want to use something public, then we can use a WebKit
bug for this (I think one already exist, but I could not find it). Link to
crbug.com/, WebKit bugs, or radars are common and you can use any of those.

[Hiroshi Ichikawa, 2017/04/28 01:30:47]

Oh I assumed that all Chromium code review URLs are public, and didn't notice
that the URL is not public. Sorry for that.

This is probably a WebKit bug for this issue, right?:
https://bugs.webkit.org/show_bug.cgi?id=134230

But its description is too short. I put both of the WebKit bug URL and Rdar URL,
but also added more words to the comment so that it is hopefully
self-explanatory.

Just curious, am I correct that content of Rdar URLs are visible to only the
reporter and Apple employees, unless the reporter copies its content to Open
Radar?

[Eugene But (OOO till 7-30), 2017/04/28 02:44:20]

Yes
 
Kind of, but not exactly :) see go/applebugs

+@property(nonatomic) UIEdgeInsets contentInset;
+
+@end
+
+#endif  // IOS_WEB_VIEW_PUBLIC_CWV_SCROLL_VIEW_H_