Revert of Overhaul Mandoline event transport code

components/pdf_viewer/pdf_viewer.cc

Index: components/pdf_viewer/pdf_viewer.cc
diff --git a/components/pdf_viewer/pdf_viewer.cc b/components/pdf_viewer/pdf_viewer.cc
index 9321668ee6d53058908bc3bf430da9390b781fba..40fbc3cb2e6a228240d55562536e19aac1adba48 100644
--- a/components/pdf_viewer/pdf_viewer.cc
+++ b/components/pdf_viewer/pdf_viewer.cc
@@ -382,20 +382,17 @@
       return;
     }
 
-    // TODO(rjkroege): Make panning and scrolling more performant and
-    // responsive to gesture events.
     if ((event->key_data &&
          event->key_data->windows_key_code == mojo::KEYBOARD_CODE_DOWN) ||
-        (event->wheel_data && event->wheel_data &&
-         event->wheel_data->delta_y < 0)) {
+        (event->pointer_data && event->pointer_data->vertical_wheel < 0)) {
       if (current_page_ < (page_count_ - 1)) {
         current_page_++;
         DrawBitmap(embedder_for_roots_[view]);
       }
     } else if ((event->key_data &&
                 event->key_data->windows_key_code == mojo::KEYBOARD_CODE_UP) ||
-               (event->pointer_data && event->wheel_data &&
-                event->wheel_data->delta_y > 0)) {
+               (event->pointer_data &&
+                event->pointer_data->vertical_wheel > 0)) {
       if (current_page_ > 0) {
         current_page_--;
         DrawBitmap(embedder_for_roots_[view]);