Lint clean video/ and add lint presubmit check.

webrtc/video/rampup_tests.cc

Index: webrtc/video/rampup_tests.cc
diff --git a/webrtc/video/rampup_tests.cc b/webrtc/video/rampup_tests.cc
index 21b442339061174394bf175c83ad053685a28afd..0e9bd3058c768aacc0e9d72cfc8293ceeca042c2 100644
--- a/webrtc/video/rampup_tests.cc
+++ b/webrtc/video/rampup_tests.cc
@@ -322,9 +322,9 @@ Call::Config RampUpDownUpTester::GetReceiverCallConfig() {
 
 std::string RampUpDownUpTester::GetModifierString() const {
   std::string str("_");
-  char temp_str[5];
-  sprintf(temp_str, "%i", static_cast<int>(num_streams_));
-  str += std::string(temp_str);
+  std::ostringstream s;
+  s << num_streams_;
+  str += s.str();
   str += "stream";
   str += (num_streams_ > 1 ? "s" : "");
   str += "_";