Handle touchpad flings with passive event listeners on compositor thread.

ui/events/blink/input_handler_proxy.cc

Index: ui/events/blink/input_handler_proxy.cc
diff --git a/ui/events/blink/input_handler_proxy.cc b/ui/events/blink/input_handler_proxy.cc
index b4e93ae46fbfcf47450ed2a6763d6c2d8d2fcf14..e1ebc38588dad79483207089a4135b0a36b1357d 100644
--- a/ui/events/blink/input_handler_proxy.cc
+++ b/ui/events/blink/input_handler_proxy.cc
@@ -21,6 +21,7 @@
 #include "ui/events/blink/did_overscroll_params.h"
 #include "ui/events/blink/input_handler_proxy_client.h"
 #include "ui/events/blink/input_scroll_elasticity_controller.h"
+#include "ui/events/blink/web_input_event_traits.h"
 #include "ui/events/latency_info.h"
 #include "ui/gfx/geometry/point_conversions.h"
 
@@ -1230,12 +1231,10 @@ bool InputHandlerProxy::TouchpadFlingScroll(
       input_handler_->GetEventListenerProperties(
           cc::EventListenerClass::kMouseWheel);
   switch (properties) {
-    case cc::EventListenerProperties::kPassive:
-      disposition = DID_HANDLE_NON_BLOCKING;
-      break;
     case cc::EventListenerProperties::kBlocking:
       disposition = DID_NOT_HANDLE;
       break;
+    case cc::EventListenerProperties::kPassive:
     case cc::EventListenerProperties::kNone: {
       WebMouseWheelEvent synthetic_wheel;
       synthetic_wheel.type = WebInputEvent::MouseWheel;
@@ -1250,6 +1249,12 @@ bool InputHandlerProxy::TouchpadFlingScroll(
       synthetic_wheel.modifiers = fling_parameters_.modifiers;
 
       disposition = ScrollByMouseWheel(synthetic_wheel);
+
+      // Send the event over to the main thread.
+      if (disposition == DID_HANDLE_NON_BLOCKING) {
+        client_->DispatchNonBlockingEventToMainThread(
+            ui::WebInputEventTraits::Clone(synthetic_wheel));
+      }
       break;
     }
     default:
@@ -1259,13 +1264,10 @@ bool InputHandlerProxy::TouchpadFlingScroll(
 
   switch (disposition) {
     case DID_HANDLE:
+    case DID_HANDLE_NON_BLOCKING:
       return true;
     case DROP_EVENT:
       break;
-    case DID_HANDLE_NON_BLOCKING:
-    // TODO(dtapuska): Process the fling on the compositor thread
-    // but post the events to the main thread; for now just pass it to the
-    // main thread.
     case DID_NOT_HANDLE:
       TRACE_EVENT_INSTANT0("input",
                            "InputHandlerProxy::scrollBy::AbortFling",