Fix ContextMenu.UnexpectedFindElementResultHandlerMessage logging.

Ensure that expected FindElementResultHandler messages do not trigger
the ContextMenu.UnexpectedFindElementResultHandlerMessage histogram.
The message should not be considered unexpected even if the message is
received after the CRWContextMenuController has cancelled showing the
context menu.

Bug: 228355
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: Iff6535420cd7a2eb8ba516f5d777c07352915852
Reviewed-on: https://chromium-review.googlesource.com/996526Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Mike Dougherty <michaeldo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548458}

ios/web/web_state/ui/crw_context_menu_controller.mm

@@ -388,7 +388,10 @@ struct ContextMenuInfo {
 
 - (void)cancelContextMenuDisplay {
   _contextMenuNeedsDisplay = NO;
-  [_pendingElementFetchRequests removeAllObjects];
+  for (HTMLElementFetchRequest* fetchRequest in _pendingElementFetchRequests
+           .allValues) {
+    [fetchRequest invalidate];
+  }
 }
 
 #pragma mark -

ios/web/web_state/ui/html_element_fetch_request.h

@@ -24,8 +24,12 @@ class TimeTicks;
     (void (^)(NSDictionary*))foundElementHandler NS_DESIGNATED_INITIALIZER;
 
 // Calls the |foundElementHandler| from the receiver's initializer with
-// |response| as the parameter.
+// |response| as the parameter. This method has no effect if |invalidate| has
+// been called.
 - (void)runHandlerWithResponse:(NSDictionary*)response;
+// Removes the stored |foundElementHandler| from the receiver's initializer.
+// |runHandlerWithResponse:| will have no effect if called after |invalidate|.
+- (void)invalidate;
 
 @end
 

ios/web/web_state/ui/html_element_fetch_request.mm

@@ -31,7 +31,13 @@
 }
 
 - (void)runHandlerWithResponse:(NSDictionary*)response {
-  _foundElementHandler(response);
+  if (_foundElementHandler) {
+    _foundElementHandler(response);
+  }
+}
+
+- (void)invalidate {
+  _foundElementHandler = nullptr;
 }
 
 @end

ios/web/web_state/ui/html_element_fetch_request_unittest.mm

@@ -45,4 +45,18 @@ TEST_F(HtmlElementFetchRequestTest, RunHandler) {
   EXPECT_NSEQ(response, received_response);
 }
 
+// Tests that |runHandlerWithResponse:| does not run the handler from the
+// object's initializer if |invalidate| has been called.
+TEST_F(HtmlElementFetchRequestTest, Invalidate) {
+  __block bool handler_called = false;
+  void (^handler)(NSDictionary*) = ^(NSDictionary* response) {
+    handler_called = true;
+  };
+  HTMLElementFetchRequest* request =
+      [[HTMLElementFetchRequest alloc] initWithFoundElementHandler:handler];
+  [request invalidate];
+  [request runHandlerWithResponse:nil];
+  EXPECT_FALSE(handler_called);
+}
+
 }  // namespace web