[Merge] Make mouse buttons 8 - 11 navigate forward and back in history

ui/events/x/events_x.cc

Index: ui/events/x/events_x.cc
diff --git a/ui/events/x/events_x.cc b/ui/events/x/events_x.cc
index 6c83976b32e4b3409b5dbf75fb90c0bf9acd97d0..1a97bc4cbb6bc248023f4c2d2b31f0dc2cc56a3f 100644
--- a/ui/events/x/events_x.cc
+++ b/ui/events/x/events_x.cc
@@ -161,6 +161,8 @@ int GetEventFlagsFromXState(unsigned int state) {
     flags |= ui::EF_MIDDLE_MOUSE_BUTTON;
   if (state & Button3Mask)
     flags |= ui::EF_RIGHT_MOUSE_BUTTON;
+  // There are no masks for EF_BACK_MOUSE_BUTTON and
+  // EF_FORWARD_MOUSE_BUTTON.
   return flags;
 }
 
@@ -224,6 +226,10 @@ int GetEventFlagsForButton(int button) {
       return ui::EF_MIDDLE_MOUSE_BUTTON;
     case 3:
       return ui::EF_RIGHT_MOUSE_BUTTON;
+    case 8:
+      return ui::EF_BACK_MOUSE_BUTTON;
+    case 9:
+      return ui::EF_FORWARD_MOUSE_BUTTON;
     default:
       return 0;
   }