Add const annotations to dispatcher

These allow us to dump the dispatcher state from other const dispatcher
methods.

Bug: 274073185
Test: m
Change-Id: I483d957b243bca595c147656d8305fdc4f43fb33
diff --git a/services/inputflinger/dispatcher/LatencyTracker.cpp b/services/inputflinger/dispatcher/LatencyTracker.cpp
index 2dd7d3f..b7c36a8 100644
--- a/services/inputflinger/dispatcher/LatencyTracker.cpp
+++ b/services/inputflinger/dispatcher/LatencyTracker.cpp
@@ -165,7 +165,7 @@
     }
 }
 
-std::string LatencyTracker::dump(const char* prefix) {
+std::string LatencyTracker::dump(const char* prefix) const {
     return StringPrintf("%sLatencyTracker:\n", prefix) +
             StringPrintf("%s  mTimelines.size() = %zu\n", prefix, mTimelines.size()) +
             StringPrintf("%s  mEventTimes.size() = %zu\n", prefix, mEventTimes.size());