Allow repeated handler removal/addition with the TouchEventQueue

ui/events/gesture_detection/bitset_32.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_EVENTS_GESTURE_DETECTION_BITSET_32_H_
 #define UI_EVENTS_GESTURE_DETECTION_BITSET_32_H_
 
 #include "base/basictypes.h"
+#include "base/logging.h"
 
 namespace ui {
 
 // Port of BitSet32 from Android
 // * platform/system/core/include/utils/BitSet.h
 // * Change-Id: I9bbf41f9d2d4a2593b0e6d7d8be7e283f985bade
 // * Please update the Change-Id as upstream Android changes are pulled.
 struct BitSet32 {
   uint32_t value;
 
   inline BitSet32() : value(0) {}
   explicit inline BitSet32(uint32_t value) : value(value) {}
 
   // Gets the value associated with a particular bit index.
-  static inline uint32_t value_for_bit(uint32_t n) { return 0x80000000 >> n; }
+  static inline uint32_t value_for_bit(uint32_t n) {
+    DCHECK_LE(n, 31U);
+    return 0x80000000 >> n;
+  }
 
   // Clears the bit set.
   inline void clear() { value = 0; }
 
   // Returns the number of marked bits in the set.
   inline uint32_t count() const { return popcnt(value); }
 
   // Returns true if the bit set does not contain any marked bits.
   inline bool is_empty() const { return !value; }
 
@@ skipping 45 matching lines @@
   // Result is undefined if all bits are unmarked.
   inline uint32_t clear_last_marked_bit() {
     uint32_t n = last_marked_bit();
     clear_bit(n);
     return n;
   }
 
   // Gets the inde of the specified bit in the set, which is the number of
   // marked bits that appear before the specified bit.
   inline uint32_t get_index_of_bit(uint32_t n) const {
+    DCHECK_LE(n, 31U);
     return popcnt(value & ~(0xffffffffUL >> n));
   }
 
   inline bool operator==(const BitSet32& other) const {
     return value == other.value;
   }
   inline bool operator!=(const BitSet32& other) const {
     return value != other.value;
   }
 
@@ skipping 20 matching lines @@
   }
   static inline uint32_t ctz(uint32_t v) {
     return popcnt((v & static_cast<uint32_t>(-static_cast<int>(v))) - 1);
   }
 #endif
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_GESTURE_DETECTION_BITSET_32_H_