Clean up dependencies for disk_cache histogram_macros.h.

chrome/browser/net/http_pipelining_compatibility_client.cc

Index: chrome/browser/net/http_pipelining_compatibility_client.cc
diff --git a/chrome/browser/net/http_pipelining_compatibility_client.cc b/chrome/browser/net/http_pipelining_compatibility_client.cc
index 4ccafbbdb2875f8d05b3c57c04fa8ce065fcc7f8..4b36dabefc05d8b2a88b021b9b3c5d64abbefa62 100644
--- a/chrome/browser/net/http_pipelining_compatibility_client.cc
+++ b/chrome/browser/net/http_pipelining_compatibility_client.cc
@@ -366,6 +366,8 @@ void HttpPipeliningCompatibilityClient::OnRequestFinished(
     int request_id, internal::PipelineTestRequest::Status status) {
   // The CACHE_HISTOGRAM_* macros are used, because they allow dynamic metric
   // names.
+  // TODO(gavinp): Clean up this dependency by moving the needed functionality
+  // into base/.
   CACHE_HISTOGRAM_ENUMERATION(GetMetricName(request_id, "Status"),
                               status,
                               internal::PipelineTestRequest::STATUS_MAX);