Use the pinch viewport offset for tap disambiguation.

Source/web/WebViewImpl.cpp

Index: Source/web/WebViewImpl.cpp
diff --git a/Source/web/WebViewImpl.cpp b/Source/web/WebViewImpl.cpp
index 32ea4c39b4ab1fa813e1725558d86faaaeec4bb4..fb1319408e8750fa7a8b241af09a204a79d513ed 100644
--- a/Source/web/WebViewImpl.cpp
+++ b/Source/web/WebViewImpl.cpp
@@ -713,20 +713,31 @@ bool WebViewImpl::handleGestureEvent(const WebGestureEvent& event)
         // Don't trigger a disambiguation popup on sites designed for mobile devices.
         // Instead, assume that the page has been designed with big enough buttons and links.
         if (event.data.tap.width > 0 && !shouldDisableDesktopWorkarounds()) {
-            // FIXME: didTapMultipleTargets should just take a rect instead of
-            // an event.
             WebGestureEvent scaledEvent = event;
             scaledEvent.x = event.x / pageScaleFactor();
             scaledEvent.y = event.y / pageScaleFactor();
             scaledEvent.data.tap.width = event.data.tap.width / pageScaleFactor();
             scaledEvent.data.tap.height = event.data.tap.height / pageScaleFactor();
-            IntRect boundingBox(scaledEvent.x - scaledEvent.data.tap.width / 2, scaledEvent.y - scaledEvent.data.tap.height / 2, scaledEvent.data.tap.width, scaledEvent.data.tap.height);
+            IntRect boundingBox(
+                scaledEvent.x - scaledEvent.data.tap.width / 2,
+                scaledEvent.y - scaledEvent.data.tap.height / 2,
+                scaledEvent.data.tap.width,
+                scaledEvent.data.tap.height);
+
+            WebSize pinchViewportOffset = pinchVirtualViewportEnabled() ?
+                flooredIntSize(page()->frameHost().pinchViewport().location()) : IntSize();
+
+            // Keep bounding box relative to the main frame.
+            boundingBox.move(pinchViewportOffset);
+
             Vector<IntRect> goodTargets;
             WillBeHeapVector<RawPtrWillBeMember<Node> > highlightNodes;
             findGoodTouchTargets(boundingBox, mainFrameImpl()->frame(), goodTargets, highlightNodes);
             // FIXME: replace touch adjustment code when numberOfGoodTargets == 1?
             // Single candidate case is currently handled by: https://bugs.webkit.org/show_bug.cgi?id=85101
-            if (goodTargets.size() >= 2 && m_client && m_client->didTapMultipleTargets(scaledEvent, goodTargets)) {
+            if (goodTargets.size() >= 2 && m_client
+                && m_client->didTapMultipleTargets(pinchViewportOffset, boundingBox, goodTargets)) {
+
                 enableTapHighlights(highlightNodes);
                 for (size_t i = 0; i < m_linkHighlights.size(); ++i)
                     m_linkHighlights[i]->startHighlightAnimationIfNeeded();