Always reset touch action at the beginning of a new gesture sequence

content/browser/renderer_host/input/input_router_impl.cc

Index: content/browser/renderer_host/input/input_router_impl.cc
diff --git a/content/browser/renderer_host/input/input_router_impl.cc b/content/browser/renderer_host/input/input_router_impl.cc
index b303acdb94cb21899d3042796cce2fe0c561ca98..af3601972cfa0cbdd854e2173b9afa9938a4516e 100644
--- a/content/browser/renderer_host/input/input_router_impl.cc
+++ b/content/browser/renderer_host/input/input_router_impl.cc
@@ -13,11 +13,11 @@
 #include "content/browser/renderer_host/input/input_router_client.h"
 #include "content/browser/renderer_host/input/touch_event_queue.h"
 #include "content/browser/renderer_host/input/touchpad_tap_suppression_controller.h"
+#include "content/browser/renderer_host/input/web_touch_event_traits.h"
 #include "content/browser/renderer_host/overscroll_controller.h"
 #include "content/common/content_constants_internal.h"
 #include "content/common/edit_command.h"
 #include "content/common/input/touch_action.h"
-#include "content/common/input/web_input_event_traits.h"
 #include "content/common/input_messages.h"
 #include "content/common/view_messages.h"
 #include "content/port/common/input_event_ack_state.h"
@@ -286,6 +286,9 @@ void InputRouterImpl::SendMouseEventImmediately(
 
 void InputRouterImpl::SendTouchEventImmediately(
     const TouchEventWithLatencyInfo& touch_event) {
+  if (WebTouchEventTraits::IsTouchSequenceStart(touch_event.event))
+    touch_action_filter_.OnTouchSequenceStart();
+
   FilterAndSendWebInputEvent(touch_event.event, touch_event.latency, false);
 }
 
@@ -335,6 +338,8 @@ bool InputRouterImpl::OnMessageReceived(const IPC::Message& message) {
 
 void InputRouterImpl::OnTouchEventAck(const TouchEventWithLatencyInfo& event,
                                       InputEventAckState ack_result) {
+  if (ack_result == INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS)
+    touch_action_filter_.OnTouchSequenceStart();

[Rick Byers, 2014/02/25 23:03:37]

I think we want to do this for TouchStart events only.  I don't think it happens
today, but in theory we could send NO_CONSUMER_EXISTS for the move/end events,
even if there's a touchstart handler.  The rationale here (which you should
probably add a comment for) should be something like "We normally watch for
touchstart events being sent to the renderer to indicate a new touch sequence,
but in some cases we may filter out sending the touchstart - so catch those
here".

Note that in the CC hit testing case you'll be double-resetting (once when the
touchstart is sent, and once when the ACK comes back), but I think that's fine
for now.  We'll probably need to revisit this when we implement touch-action
support in the CC (since then we could get a NO_CONSUMER_EXISTS ACK AND still
have a touch-action other than auto).

[tdresser, 2014/02/26 14:04:49]

Done.

[Rick Byers, 2014/02/26 14:32:33]

nit: since the assumptions here may change in the future, please add a comment
explaining the current rationale.

[tdresser, 2014/02/26 15:16:13]

Whoops, sorry.
Done.

   ack_handler_->OnTouchEventAck(event, ack_result);
 }