Misc fixes for gn builds with VS 2015

gpu/command_buffer/client/query_tracker.cc

Index: gpu/command_buffer/client/query_tracker.cc
diff --git a/gpu/command_buffer/client/query_tracker.cc b/gpu/command_buffer/client/query_tracker.cc
index ec678a261c7e51e006db0a9d5b7acfbb1a8fcd3f..f5363f0a2ad73fc96061bb577df862198e04550d 100644
--- a/gpu/command_buffer/client/query_tracker.cc
+++ b/gpu/command_buffer/client/query_tracker.cc
@@ -67,7 +67,7 @@ bool QuerySyncManager::Alloc(QuerySyncManager::QueryInfo* info) {
     buckets_.push_back(bucket);
   }
 
-  unsigned short index_in_bucket = 0;
+  size_t index_in_bucket = 0;
   for (size_t i = 0; i < kSyncsPerBucket; i++) {
     if (!bucket->in_use_queries[i]) {
       index_in_bucket = i;