Change some ints to size_t to fix warning on win64 builds

chrome/renderer/safe_browsing/threat_dom_details.cc

Index: chrome/renderer/safe_browsing/threat_dom_details.cc
diff --git a/chrome/renderer/safe_browsing/threat_dom_details.cc b/chrome/renderer/safe_browsing/threat_dom_details.cc
index 7d715f15acd6d0be4fe7e7a3e0d2ac8030669f2b..777167b56b53097d5aa1d3573746b8cac147b4d5 100644
--- a/chrome/renderer/safe_browsing/threat_dom_details.cc
+++ b/chrome/renderer/safe_browsing/threat_dom_details.cc
@@ -32,7 +32,7 @@ namespace safe_browsing {
 // copied into the map when inserting new elements.
 // The values are indices into the resource vector, and are used to retrieve IPC
 // messages generated by ThreatDOMDetails.
-using ElementToNodeMap = std::map<blink::WebNode, int>;
+using ElementToNodeMap = std::map<blink::WebNode, size_t>;
 
 // This Feature specifies which non-resource HTML Elements to collect based on
 // their tag and attributes. It's a single param containing a comma-separated
@@ -171,7 +171,7 @@ void HandleElement(
   // Update the ID mapping. First generate the ID for the current node.
   // Then, if its parent is available, set the current node's parent ID, and
   // also update the parent's children with the current node's ID.
-  const int child_id = element_to_node_map->size() + 1;
+  const size_t child_id = element_to_node_map->size() + 1;
   child_node.node_id = child_id;
   blink::WebNode cur_parent_element = element.parentNode();
   while (!cur_parent_element.isNull()) {