surfaceflinger: Avoid extra vector copies

We pass a std::vector by const reference in a couple places in
TransactionCompletedThread to avoid making an extra copy.

Test: TreeHugger
Change-Id: Ie81a27b80e52a1890d54b4507d0fcbf30e746e7b
diff --git a/services/surfaceflinger/TransactionCompletedThread.cpp b/services/surfaceflinger/TransactionCompletedThread.cpp
index 1d2217d..6b2b583 100644
--- a/services/surfaceflinger/TransactionCompletedThread.cpp
+++ b/services/surfaceflinger/TransactionCompletedThread.cpp
@@ -34,7 +34,8 @@
 //         >0 if the first id that doesn't match is greater in c2 or all ids match but c2 is longer
 //
 // See CallbackIdsHash for a explaniation of why this works
-static int compareCallbackIds(const std::vector<CallbackId>& c1, const std::vector<CallbackId> c2) {
+static int compareCallbackIds(const std::vector<CallbackId>& c1,
+                              const std::vector<CallbackId>& c2) {
     if (c1.empty()) {
         return !c2.empty();
     }