input: Use set::find to accelerate the finding process

This CL uses a set::find overload to use the uint32_t type to find
the object to avoid construct another object.

By following the style guide, added a comparator struct.
"For example, if your type doesn't have a natural ordering,
but you want to store it in a std::set, use a custom comparator
rather than overloading <."
https://google.github.io/styleguide/cppguide.html#Operator_Overloading

Bug: None
Change-Id: Ic8b9f51a3b3a50601b1ecfa1ba8039ecf16a22ee
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2358449Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Commit-Queue: Shimi Zhang <ctzsm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#798823}

content/browser/renderer_host/input/passthrough_touch_event_queue.cc

@@ -54,11 +54,6 @@ PassthroughTouchEventQueue::TouchEventWithLatencyInfoAndAckState::
     : TouchEventWithLatencyInfo(event),
       ack_state_(blink::mojom::InputEventResultState::kUnknown) {}
 
-bool PassthroughTouchEventQueue::TouchEventWithLatencyInfoAndAckState::
-operator<(const TouchEventWithLatencyInfoAndAckState& other) const {
-  return event.unique_touch_event_id < other.event.unique_touch_event_id;
-}
-
 PassthroughTouchEventQueue::PassthroughTouchEventQueue(
     PassthroughTouchEventQueueClient* client,
     const Config& config)
@@ -136,13 +131,7 @@ void PassthroughTouchEventQueue::ProcessTouchAck(
                                           should_stop_timeout_monitor))
     return;
 
-  auto touch_event_iter = outstanding_touches_.begin();
-  while (touch_event_iter != outstanding_touches_.end()) {
-    if (unique_touch_event_id == touch_event_iter->event.unique_touch_event_id)
-      break;
-    ++touch_event_iter;
-  }
-
+  auto touch_event_iter = outstanding_touches_.find(unique_touch_event_id);
   if (touch_event_iter == outstanding_touches_.end())
     return;
 

content/browser/renderer_host/input/passthrough_touch_event_queue.h

@@ -172,7 +172,6 @@ class CONTENT_EXPORT PassthroughTouchEventQueue {
       : public TouchEventWithLatencyInfo {
    public:
     TouchEventWithLatencyInfoAndAckState(const TouchEventWithLatencyInfo&);
-    bool operator<(const TouchEventWithLatencyInfoAndAckState&) const;
     blink::mojom::InputEventResultState ack_state() const { return ack_state_; }
     blink::mojom::InputEventResultSource ack_source() const {
       return ack_source_;
@@ -188,6 +187,22 @@ class CONTENT_EXPORT PassthroughTouchEventQueue {
     blink::mojom::InputEventResultState ack_state_;
   };
 
+  struct TouchEventWithLatencyInfoAndAckStateComparator {
+    using is_transparent = void;
+    bool operator()(const TouchEventWithLatencyInfoAndAckState& lhs,
+                    const TouchEventWithLatencyInfoAndAckState& rhs) const {
+      return lhs.event.unique_touch_event_id < rhs.event.unique_touch_event_id;
+    }
+    bool operator()(const TouchEventWithLatencyInfoAndAckState& lhs,
+                    const uint32_t rhs) const {
+      return lhs.event.unique_touch_event_id < rhs;
+    }
+    bool operator()(const uint32_t lhs,
+                    const TouchEventWithLatencyInfoAndAckState& rhs) const {
+      return lhs < rhs.event.unique_touch_event_id;
+    }
+  };
+
   // These values are logged to UMA. Entries should not be renumbered and
   // numeric values should never be reused. Please keep in sync with
   // "EventPreFilterResult" in src/tools/metrics/histograms/enums.xml.
@@ -248,7 +263,9 @@ class CONTENT_EXPORT PassthroughTouchEventQueue {
   // Stores outstanding touches that have been sent to the renderer but have
   // not yet been ack'd by the renderer. The set is explicitly ordered based
   // on the unique touch event id.
-  std::set<TouchEventWithLatencyInfoAndAckState> outstanding_touches_;
+  std::set<TouchEventWithLatencyInfoAndAckState,
+           TouchEventWithLatencyInfoAndAckStateComparator>
+      outstanding_touches_;
 
   // Whether we should allow events to bypass normal queue filter rules.
   const bool skip_touch_filter_;