Show the Chrome context menu when running on iOS 11.

Bring back an old hack to prioritize our gesture recognizer over
WKWebView's when running on iOS 11 or later. The hack was previously
removed in
https://codereview.chromium.org/2627093003/patch/160001/170008.

Bug: 736330, 736480
Change-Id: I669a3d530942e39db246f9b298a5f7a797e9754b
Reviewed-on: https://chromium-review.googlesource.com/585672
Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Mike Dougherty <michaeldo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491040}

ios/web/web_state/ui/crw_context_menu_controller.mm

@@ -7,6 +7,7 @@
 #import <objc/runtime.h>
 #include <stddef.h>
 
+#include "base/ios/ios_util.h"
 #include "base/logging.h"
 #include "base/mac/foundation_util.h"
 #include "base/metrics/histogram_macros.h"
@@ -54,6 +55,9 @@ @interface CRWContextMenuController ()<UIGestureRecognizerDelegate>
 // Returns the x, y offset the content has been scrolled.
 @property(nonatomic, readonly) CGPoint scrollPosition;
 
+// Returns a gesture recognizers with |fragment| in it's description.
+- (UIGestureRecognizer*)gestureRecognizerWithDescriptionFragment:
+    (NSString*)fragment;
 // Called when the window has determined there was a long-press and context menu
 // must be shown.
 - (void)showContextMenu:(UIGestureRecognizer*)gestureRecognizer;
@@ -107,10 +111,46 @@ - (instancetype)initWithWebView:(WKWebView*)webView
     [_contextMenuRecognizer setAllowableMovement:kLongPressMoveDeltaPixels];
     [_contextMenuRecognizer setDelegate:self];
     [_webView addGestureRecognizer:_contextMenuRecognizer];
+
+    if (base::ios::IsRunningOnIOS11OrLater()) {
+      // WKWebView's default context menu gesture recognizer interferes with
+      // the detection of a long press by |_contextMenuRecognizer|. WKWebView's
+      // context menu gesture recognizer should fail if |_contextMenuRecognizer|
+      // detects a long press.
+      NSString* fragment = @"action=_longPressRecognized:";
+      UIGestureRecognizer* systemContextMenuRecognizer =
+          [self gestureRecognizerWithDescriptionFragment:fragment];
+      if (systemContextMenuRecognizer) {
+        [systemContextMenuRecognizer
+            requireGestureRecognizerToFail:_contextMenuRecognizer];
+        // requireGestureRecognizerToFail: doesn't retain the recognizer, so it
+        // is possible for |iRecognizer| to outlive |recognizer| and end up with
+        // a dangling pointer. Add a retaining associative reference to ensure
+        // that the lifetimes work out.
+        // Note that normally using the value as the key wouldn't make any
+        // sense, but here it's fine since nothing needs to look up the value.
+        void* associated_object_key = (__bridge void*)_contextMenuRecognizer;
+        objc_setAssociatedObject(systemContextMenuRecognizer.view,
+                                 associated_object_key, _contextMenuRecognizer,
+                                 OBJC_ASSOCIATION_RETAIN_NONATOMIC);
+      }
+    }
   }
   return self;
 }
 
+- (UIGestureRecognizer*)gestureRecognizerWithDescriptionFragment:
+    (NSString*)fragment {
+  for (UIView* view in [[_webView scrollView] subviews]) {
+    for (UIGestureRecognizer* recognizer in [view gestureRecognizers]) {
+      if ([recognizer.description rangeOfString:fragment].length) {
+        return recognizer;
+      }
+    }
+  }
+  return nil;
+}
+
 - (UIScrollView*)webScrollView {
   return [_webView scrollView];
 }