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}
std::unique_ptr<HistogramBase> Histogram::PersistentCreate(
    const std::string& name,
    Sample minimum,
    Sample maximum,
    const BucketRanges* ranges,
    HistogramBase::AtomicCount* counts,
    HistogramBase::AtomicCount* logged_counts,
    uint32_t counts_size,
    HistogramSamples::Metadata* meta,
    HistogramSamples::Metadata* logged_meta) {
  return WrapUnique(new Histogram(name, minimum, maximum, ranges, counts,
                                  logged_counts, counts_size, meta,
                                  logged_meta));
}

std::unique_ptr<HistogramBase> Histogram::PersistentCreate(
    const std::string& name,
    Sample minimum,
    Sample maximum,
    const BucketRanges* ranges,
    HistogramBase::AtomicCount* counts,
    HistogramBase::AtomicCount* logged_counts,
    uint32_t counts_size,
    HistogramSamples::Metadata* meta,
    HistogramSamples::Metadata* logged_meta) {
  return WrapUnique(new Histogram(name, minimum, maximum, ranges, counts,
                                  logged_counts, counts_size, meta,
                                  logged_meta));
}
