Convert DCHECKs to CHECKs for histogram types

When a histogram is looked up by name, there is currently a DCHECK that
verifies the type of the stored histogram matches the expected type.

A mismatch represents a significant problem because the returned
HistogramBase is cast to a Histogram in ValidateRangeChecksum,
potentially causing a crash.

This CL converts the DCHECK to a CHECK to prevent the possibility of
type confusion in release builds.

BUG=651443
R=isherman@chromium.org

Review-Url: https://codereview.chromium.org/2381893003
Cr-Commit-Position: refs/heads/master@{#421929}
bool Histogram::SerializeInfoImpl(Pickle* pickle) const {
  DCHECK(bucket_ranges()->HasValidChecksum());
  return pickle->WriteString(histogram_name()) &&
      pickle->WriteInt(flags()) &&
      pickle->WriteInt(declared_min()) &&
      pickle->WriteInt(declared_max()) &&
      pickle->WriteUInt32(bucket_count()) &&
      pickle->WriteUInt32(bucket_ranges()->checksum());
}

bool Histogram::SerializeInfoImpl(Pickle* pickle) const {
  DCHECK(bucket_ranges()->HasValidChecksum());
  return pickle->WriteString(histogram_name()) &&
      pickle->WriteInt(flags()) &&
      pickle->WriteInt(declared_min()) &&
      pickle->WriteInt(declared_max()) &&
      pickle->WriteUInt32(bucket_count()) &&
      pickle->WriteUInt32(bucket_ranges()->checksum());
}
