Make ScrollUpdate LatencyInfo's sequence number less likely to have conflicts

cc/trees/latency_info_swap_promise_monitor.cc

Index: cc/trees/latency_info_swap_promise_monitor.cc
diff --git a/cc/trees/latency_info_swap_promise_monitor.cc b/cc/trees/latency_info_swap_promise_monitor.cc
index 286d6dbd8fa12376dcca7a7fa88049c9403c8b80..80ad76d0d9ded2708d9d4fa15a90ace78f11ce42 100644
--- a/cc/trees/latency_info_swap_promise_monitor.cc
+++ b/cc/trees/latency_info_swap_promise_monitor.cc
@@ -71,9 +71,11 @@ void LatencyInfoSwapPromiseMonitor::OnForwardScrollUpdateToMainThreadOnImpl() {
          it != latency_->latency_components.end(); ++it) {
       if (it->first.first == ui::INPUT_EVENT_LATENCY_BEGIN_RWH_COMPONENT) {
         new_sequence_number =
-            (static_cast<int64>(base::PlatformThread::CurrentId()) << 32) |
+            ((static_cast<int64>(base::PlatformThread::CurrentId()) << 32) ^
+             (std::abs(reinterpret_cast<int64>(this)) << 32)) |

[Sami, 2015/04/16 10:55:44]

Could you replace the abs() with a cast to uint64 before shifting?

[Yufeng Shen (Slow to review), 2015/04/16 15:19:54]

Done.

             (it->second.sequence_number & 0xffffffff);
-        DCHECK(new_sequence_number != it->second.sequence_number);
+        if (new_sequence_number == it->second.sequence_number)
+          return;
         break;
       }
     }