Update RateStatistics to handle too-little-data case.

webrtc/common_video/bitrate_adjuster_unittest.cc

 /*
  *  Copyright 2016 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 30 matching lines @@
 
   uint32_t GetTargetBitrateBpsPct(float pct) {
     return pct * adjuster_.GetTargetBitrateBps();
   }
 
   void VerifyAdjustment() {
     // The adjusted bitrate should be between the estimated bitrate and the
     // target bitrate within clamp.
     uint32_t target_bitrate_bps = adjuster_.GetTargetBitrateBps();
     uint32_t adjusted_bitrate_bps = adjuster_.GetAdjustedBitrateBps();
-    uint32_t estimated_bitrate_bps = adjuster_.GetEstimatedBitrateBps();
+    uint32_t estimated_bitrate_bps =
+        adjuster_.GetEstimatedBitrateBps().value_or(target_bitrate_bps);
     uint32_t adjusted_lower_bound_bps =
         GetTargetBitrateBpsPct(kMinAdjustedBitratePct);
     uint32_t adjusted_upper_bound_bps =
         GetTargetBitrateBpsPct(kMaxAdjustedBitratePct);
     EXPECT_LE(adjusted_bitrate_bps, adjusted_upper_bound_bps);
     EXPECT_GE(adjusted_bitrate_bps, adjusted_lower_bound_bps);
     if (estimated_bitrate_bps > target_bitrate_bps) {
       EXPECT_LT(adjusted_bitrate_bps, target_bitrate_bps);
     }
   }
@@ skipping 97 matching lines @@
   EXPECT_EQ(initial_target_bitrate_bps, adjuster_.GetAdjustedBitrateBps());
 
   // 1.05 * 1.05 is 1.1 which is greater than tolerance for the initial target
   // bitrate. Since we didn't advance the clock the adjuster never updated.
   target_bitrate_bps = (1 + delta_pct) * target_bitrate_bps;
   adjuster_.SetTargetBitrateBps(target_bitrate_bps);
   EXPECT_EQ(target_bitrate_bps, adjuster_.GetAdjustedBitrateBps());
 }
 
 }  // namespace webrtc