Add Precache.Fetch.MinWeight UMA.

components/precache/core/precache_fetcher.h

Index: components/precache/core/precache_fetcher.h
diff --git a/components/precache/core/precache_fetcher.h b/components/precache/core/precache_fetcher.h
index 9868d1c015a84d0f26922e4971f162cb5dd8f389..020a8413e53900cd9d35fc552b5c508e70f4b0cb 100644
--- a/components/precache/core/precache_fetcher.h
+++ b/components/precache/core/precache_fetcher.h
@@ -17,6 +17,7 @@
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
+#include "base/optional.h"
 #include "base/single_thread_task_runner.h"
 #include "base/time/time.h"
 #include "components/precache/core/fetcher_pool.h"
@@ -136,7 +137,8 @@ class PrecacheFetcher : public base::SupportsWeakPtr<PrecacheFetcher> {
   static void RecordCompletionStatistics(
       const PrecacheUnfinishedWork& unfinished_work,
       size_t remaining_manifest_urls_to_fetch,
-      size_t remaining_resource_urls_to_fetch);
+      size_t remaining_resource_urls_to_fetch,
+      base::Optional<double> min_weight_fetched);
 
   static std::string GetResourceURLBase64HashForTesting(
       const std::vector<GURL>& urls);
@@ -179,7 +181,8 @@ class PrecacheFetcher : public base::SupportsWeakPtr<PrecacheFetcher> {
   // Notifies the precache delete that precaching is done, and report
   // completion statistics.
   void NotifyDone(size_t remaining_manifest_urls_to_fetch,
-                  size_t remaining_resource_urls_to_fetch);
+                  size_t remaining_resource_urls_to_fetch,
+                  base::Optional<double> min_weight_fetched);
 
   // Fetches the next resource or manifest URL, if any remain. Fetching is done
   // sequentially and depth-first: all resources are fetched for a manifest