Remove minimum bucket returned by histogram quantile function.

This fixes a bug in delay manager relative arrival delay mode that caused the effective minimum target level to be 2 packets instead of 1.

Bug: webrtc:10333
Change-Id: I33d32c8da692a3db22179edb923873d307f740fd
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/150785
Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org>
Reviewed-by: Minyue Li <minyue@webrtc.org>
Commit-Queue: Jakob Ivarsson <jakobi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29002}
diff --git a/modules/audio_coding/neteq/histogram.cc b/modules/audio_coding/neteq/histogram.cc
index 99ea9aa..d0da16b 100644
--- a/modules/audio_coding/neteq/histogram.cc
+++ b/modules/audio_coding/neteq/histogram.cc
@@ -116,14 +116,14 @@
   int inverse_probability = (1 << 30) - probability;
   size_t index = 0;        // Start from the beginning of |buckets_|.
   int sum = 1 << 30;       // Assign to 1 in Q30.
-  sum -= buckets_[index];  // Ensure that target level is >= 1.
+  sum -= buckets_[index];
 
-  do {
+  while ((sum > inverse_probability) && (index < buckets_.size() - 1)) {
     // Subtract the probabilities one by one until the sum is no longer greater
     // than |inverse_probability|.
     ++index;
     sum -= buckets_[index];
-  } while ((sum > inverse_probability) && (index < buckets_.size() - 1));
+  }
   return static_cast<int>(index);
 }