Fix some signed overflow errors causing undefined behavior (in theory).

webrtc/base/rollingaccumulator.h

 /*
  *  Copyright 2011 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 38 matching lines @@
     max_stale_ = false;
     min_ = T();
     min_stale_ = false;
   }
 
   void AddSample(T sample) {
     if (count_ == max_count()) {
       // Remove oldest sample.
       T sample_to_remove = samples_[next_index_];
       sum_ -= sample_to_remove;
-      sum_2_ -= sample_to_remove * sample_to_remove;
+      sum_2_ -= static_cast<double>(sample_to_remove) * sample_to_remove;
       if (sample_to_remove >= max_) {
         max_stale_ = true;
       }
       if (sample_to_remove <= min_) {
         min_stale_ = true;
       }
     } else {
       // Increase count of samples.
       ++count_;
     }
     // Add new sample.
     samples_[next_index_] = sample;
     sum_ += sample;
-    sum_2_ += sample * sample;
+    sum_2_ += static_cast<double>(sample) * sample;
     if (count_ == 1 || sample >= max_) {
       max_ = sample;
       max_stale_ = false;
     }
     if (count_ == 1 || sample <= min_) {
       min_ = sample;
       min_stale_ = false;
     }
     // Update next_index_.
     next_index_ = (next_index_ + 1) % max_count();
@@ skipping 80 matching lines @@
   mutable T min_;
   mutable bool min_stale_;
   std::vector<T> samples_;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(RollingAccumulator);
 };
 
 }  // namespace rtc
 
 #endif  // WEBRTC_BASE_ROLLINGACCUMULATOR_H_