[ObjC ARC] Converts ios/web:web to ARC.

ios/web/web_state/ui/crw_web_view_content_view.mm

Index: ios/web/web_state/ui/crw_web_view_content_view.mm
diff --git a/ios/web/web_state/ui/crw_web_view_content_view.mm b/ios/web/web_state/ui/crw_web_view_content_view.mm
index cda73439b3d0f42c8103772e1e7ee1dfc7b1d2df..32aac34b93d43ffdccacce03efb885486ff80b34 100644
--- a/ios/web/web_state/ui/crw_web_view_content_view.mm
+++ b/ios/web/web_state/ui/crw_web_view_content_view.mm
@@ -7,7 +7,10 @@
 #import <WebKit/WebKit.h>
 
 #include "base/logging.h"
-#import "base/mac/scoped_nsobject.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
 
 namespace {
 
@@ -21,10 +24,6 @@ const CGFloat kBackgroundRGBComponents[] = {0.75f, 0.74f, 0.76f};
 }  // namespace
 
 @interface CRWWebViewContentView () {
-  // The web view being shown.
-  base::scoped_nsobject<UIView> _webView;
-  // The web view's scroll view.
-  base::scoped_nsobject<UIScrollView> _scrollView;
   // Backs up property of the same name if |_webView| is a WKWebView.
   CGFloat _topContentPadding;
 }
@@ -33,11 +32,17 @@ const CGFloat kBackgroundRGBComponents[] = {0.75f, 0.74f, 0.76f};
 // |_topContentPadding| (iff |_webView| is a WKWebView).
 - (void)updateWebViewFrame;
 
+// The web view being shown.
+@property(nonatomic, strong, readwrite) UIView* webView;
+// The web view's scroll view.
+@property(nonatomic, strong, readwrite) UIScrollView* scrollView;
 @end
 
 @implementation CRWWebViewContentView
 
 @synthesize shouldUseInsetForTopPadding = _shouldUseInsetForTopPadding;
+@synthesize webView = _webView;
+@synthesize scrollView = _scrollView;
 
 - (instancetype)initWithWebView:(UIView*)webView
                      scrollView:(UIScrollView*)scrollView {
@@ -46,8 +51,8 @@ const CGFloat kBackgroundRGBComponents[] = {0.75f, 0.74f, 0.76f};
     DCHECK(webView);
     DCHECK(scrollView);
     DCHECK([scrollView isDescendantOfView:webView]);
-    _webView.reset([webView retain]);
-    _scrollView.reset([scrollView retain]);
+    _webView = webView;
+    _scrollView = scrollView;
   }
   return self;
 }
@@ -97,16 +102,6 @@ const CGFloat kBackgroundRGBComponents[] = {0.75f, 0.74f, 0.76f};
   [self updateWebViewFrame];
 }
 
-#pragma mark Accessors
-
-- (UIScrollView*)scrollView {
-  return _scrollView.get();
-}
-
-- (UIView*)webView {
-  return _webView.get();
-}
-
 #pragma mark Layout
 
 - (void)layoutSubviews {