Let CWVWebView.scrollView be typed UIScrollView.

It is now implemented as a proxy object (CRWWebViewScrollViewProxy)
which pretends itself to be a UIScrollView, instead of CWVScrollView.

Define CWVWebView.legacyScrollView to allow to fall back to the original
implementation in runtime temporarily.

Change-Id: I2993ab2ccf78de09412c9f607a74165fea8eae2f
Bug: 1023250
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2137201
Commit-Queue: Hiroshi Ichikawa <ichikawa@chromium.org>
Auto-Submit: Hiroshi Ichikawa <ichikawa@chromium.org>
Reviewed-by: John Wu <jzw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#762718}

ios/web_view/internal/cwv_web_view.mm

@@ -177,7 +177,7 @@ BOOL gChromeLongPressAndForceTouchHandlingEnabled = YES;
 @synthesize title = _title;
 @synthesize translationController = _translationController;
 @synthesize UIDelegate = _UIDelegate;
-@synthesize scrollView = _scrollView;
+@synthesize legacyScrollView = _legacyScrollView;
 @synthesize visibleURL = _visibleURL;
 @synthesize visibleSSLStatus = _visibleSSLStatus;
 
@@ -243,7 +243,7 @@ BOOL gChromeLongPressAndForceTouchHandlingEnabled = YES;
   if (self) {
     _configuration = configuration;
     [_configuration registerWebView:self];
-    _scrollView = [[CWVScrollView alloc] init];
+    _legacyScrollView = [[CWVScrollView alloc] init];
 
     [self resetWebStateWithSessionStorage:nil
                           WKConfiguration:wkConfiguration
@@ -252,6 +252,10 @@ BOOL gChromeLongPressAndForceTouchHandlingEnabled = YES;
   return self;
 }
 
+- (UIScrollView*)scrollView {
+  return [_webState->GetWebViewProxy().scrollViewProxy asUIScrollView];
+}
+
 - (BOOL)allowsBackForwardNavigationGestures {
   return _webState->GetWebViewProxy().allowsBackForwardNavigationGestures;
 }
@@ -809,7 +813,7 @@ BOOL gChromeLongPressAndForceTouchHandlingEnabled = YES;
   _webState->GetWebViewProxy().allowsBackForwardNavigationGestures =
       allowsBackForwardNavigationGestures;
 
-  _scrollView.proxy = _webState.get()->GetWebViewProxy().scrollViewProxy;
+  _legacyScrollView.proxy = _webState.get()->GetWebViewProxy().scrollViewProxy;
 
   if (_translationController) {
     id<CWVTranslationControllerDelegate> delegate =

ios/web_view/public/cwv_web_view.h

@@ -111,7 +111,17 @@ CWV_EXPORT
 @property(nonatomic, readonly) double estimatedProgress;
 
 // The scroll view associated with the web view.
-@property(nonatomic, readonly) CWVScrollView* scrollView;
+//
+// It is reset on state restoration.
+@property(nonatomic, readonly) UIScrollView* scrollView;
+
+// DEPRECATED: Use |scrollView| instead.
+//
+// The old implementation of the scroll view associated with the web view.
+//
+// TODO(crbug.com/1023250): Delete this once clients migrate to the new
+// |scrollView|.
+@property(nonatomic, readonly) CWVScrollView* legacyScrollView;
 
 // A Boolean value indicating whether horizontal swipe gestures will trigger
 // back-forward list navigations.

ios/web_view/shell/shell_view_controller.m

@@ -21,12 +21,13 @@ NSString* const kWebViewShellAddressFieldAccessibilityLabel = @"Address field";
 NSString* const kWebViewShellJavaScriptDialogTextFieldAccessibilityIdentifier =
     @"WebViewShellJavaScriptDialogTextFieldAccessibilityIdentifier";
 
-@interface ShellViewController ()<CWVDownloadTaskDelegate,
-                                  CWVNavigationDelegate,
-                                  CWVUIDelegate,
-                                  CWVScriptCommandHandler,
-                                  CWVSyncControllerDelegate,
-                                  UITextFieldDelegate>
+@interface ShellViewController () <CWVDownloadTaskDelegate,
+                                   CWVNavigationDelegate,
+                                   CWVUIDelegate,
+                                   CWVScriptCommandHandler,
+                                   CWVSyncControllerDelegate,
+                                   UIScrollViewDelegate,
+                                   UITextFieldDelegate>
 // Header containing navigation buttons and |field|.
 @property(nonatomic, strong) UIView* headerBackgroundView;
 // Header containing navigation buttons and |field|.
@@ -268,6 +269,14 @@ NSString* const kWebViewShellJavaScriptDialogTextFieldAccessibilityIdentifier =
   self.webView = [self createWebViewWithConfiguration:configuration];
 }
 
+- (void)applicationFinishedRestoringState {
+  [super applicationFinishedRestoringState];
+
+  // The scroll view is reset on state restoration. So the delegate must be
+  // reassigned.
+  self.webView.scrollView.delegate = self;
+}
+
 - (UIStatusBarStyle)preferredStatusBarStyle {
   return UIStatusBarStyleLightContent;
 }
@@ -682,6 +691,7 @@ NSString* const kWebViewShellJavaScriptDialogTextFieldAccessibilityIdentifier =
   webView.translationController.delegate = _translationDelegate;
   _autofillDelegate = [[ShellAutofillDelegate alloc] init];
   webView.autofillController.delegate = _autofillDelegate;
+  webView.scrollView.delegate = self;
 
   // Constraints.
   webView.translatesAutoresizingMaskIntoConstraints = NO;
@@ -1125,4 +1135,10 @@ NSString* const kWebViewShellJavaScriptDialogTextFieldAccessibilityIdentifier =
   NSLog(@"%@", NSStringFromSelector(_cmd));
 }
 
+#pragma mark UIScrollViewDelegate
+
+- (void)scrollViewWillBeginDragging:(UIScrollView*)scrollView {
+  NSLog(@"%@", NSStringFromSelector(_cmd));
+}
+
 @end