Consuming a touch move prevents only the next scroll update.

content/browser/renderer_host/input/touch_disposition_gesture_filter.h

Index: content/browser/renderer_host/input/touch_disposition_gesture_filter.h
diff --git a/content/browser/renderer_host/input/touch_disposition_gesture_filter.h b/content/browser/renderer_host/input/touch_disposition_gesture_filter.h
index f2acc3b47c1b1ab6001cd16fa4f1315264baa3a3..649fd9d1a296c82f01b622ef152075ca53c3064f 100644
--- a/content/browser/renderer_host/input/touch_disposition_gesture_filter.h
+++ b/content/browser/renderer_host/input/touch_disposition_gesture_filter.h
@@ -5,14 +5,24 @@
 #ifndef CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_DISPOSITION_GESTURE_FILTER_H_
 #define CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_DISPOSITION_GESTURE_FILTER_H_
 
-#include <deque>
 #include <queue>
+#include <set>
 
 #include "content/browser/renderer_host/input/gesture_event_packet.h"
 #include "content/common/content_export.h"
 #include "content/port/common/input_event_ack_state.h"
 #include "third_party/WebKit/public/web/WebInputEvent.h"
 
+namespace {
+
+enum RequiredTouches {

[jdduke (slow), 2014/02/14 16:59:52]

Any reason we can't stick this in the .cc file?

[tdresser, 2014/02/14 17:56:11]

Done.

+  RT_NONE    = 0,
+  RT_START   = 1 << 0,
+  RT_CURRENT = 1 << 1,
+};
+
+}  // namespace
+
 namespace content {
 
 // Interface with which the |TouchDispositionGestureFilter| forwards gestures
@@ -56,30 +66,45 @@ class CONTENT_EXPORT TouchDispositionGestureFilter {
   // generated by timeouts from a statinoary finger.
   class GestureSequence {
    public:
+    struct GestureHandlingState {
+      GestureHandlingState();
+      // True iff the sequence has had at least one touch acked.
+      bool seen_ack;
+      // True iff the sequence has had any touch down event consumed.
+      bool start_consumed;
+      // True iff the first ack received for this sequence reported that no
+      // consumer exists.
+      bool no_consumer;
+    };
+
     GestureSequence();
     ~GestureSequence();
 
     void Push(const GestureEventPacket& packet);
     void Pop();
     const GestureEventPacket& Front() const;
-    void UpdateState(InputEventAckState ack_state);
-    bool IsGesturePrevented() const;
+    void UpdateState(GestureEventPacket::GestureSource gesture_source,
+                     InputEventAckState ack_state);
     bool IsEmpty() const;
+    const GestureHandlingState& state() const { return state_; };
 
    private:
     std::queue<GestureEventPacket> packets_;
-    enum GestureHandlingState {
-      PENDING,                 // The sequence has yet to receive an ack.
-      ALLOWED_UNTIL_PREVENTED, // Gestures in the sequence are allowed until
-                               // a source touch is preventDefault'ed.
-      ALWAYS_ALLOWED,          // All remaining sequence gestures are forwarded.
-      ALWAYS_PREVENTED         // All remaining sequence gestures are dropped.
-    };
     GestureHandlingState state_;
   };
+  bool IsGesturePrevented(blink::WebInputEvent::Type type,
+                          InputEventAckState current,
+                          const GestureSequence::GestureHandlingState& state)
+      const;
+
   void UpdateAndDispatchPackets(GestureSequence* sequence,
                                 InputEventAckState ack_result);
-  void SendPacket(const GestureEventPacket& packet);
+
+  void FilterAndSendPacket(
+      const GestureEventPacket& packet,
+      const GestureSequence::GestureHandlingState& sequence_state,
+      InputEventAckState ack_state);
+
   void SendGesture(const blink::WebGestureEvent& gesture);
   void CancelTapIfNecessary();
   void CancelFlingIfNecessary();
@@ -89,6 +114,11 @@ class CONTENT_EXPORT TouchDispositionGestureFilter {
   TouchDispositionGestureFilterClient* client_;
   std::queue<GestureSequence> sequences_;
 
+  // If the previous gesture of a given type was dropped instead of being
+  // dispatched, its type will occur in this set. Cleared when a new touch
+  // sequence begins to be acked.
+  std::set<blink::WebInputEvent::Type> last_event_of_type_dropped_;
+
   // Bookkeeping for inserting synthetic Gesture{Tap,Fling}Cancel events
   // when necessary, e.g., GestureTapCancel when scrolling begins, or
   // GestureFlingCancel when a user taps following a GestureFlingStart.