Android history reports: switch iterator to range-based for loop.

Change-Id: Ib37c918d0e96be88c51e5ce3a06f2d1e39ba3f75
Reviewed-on: https://chromium-review.googlesource.com/1100678Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Commit-Queue: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567364}

chrome/browser/android/history_report/usage_reports_buffer_backend.cc

@@ -109,10 +109,8 @@ void UsageReportsBufferBackend::Remove(
   // TODO(haaawk): investigate if it's worth sorting the keys here to improve
   // performance.
   leveldb::WriteBatch updates;
-  for (std::vector<std::string>::const_iterator it = reports.begin();
-       it != reports.end();
-       ++it) {
-    updates.Delete(leveldb::Slice(*it));
+  for (const auto& report : reports) {
+    updates.Delete(leveldb::Slice(report));
   }
 
   leveldb::WriteOptions write_options;