Gather metrics on hosted app unlimitedStorage usage

extensions/browser/api/storage/local_value_store_cache.cc

Index: extensions/browser/api/storage/local_value_store_cache.cc
diff --git a/extensions/browser/api/storage/local_value_store_cache.cc b/extensions/browser/api/storage/local_value_store_cache.cc
index 4865b31ed0206459fe190e010be8cb170a5b8e91..df183b994fb7d88ff90934e78fa868f95adbb060 100644
--- a/extensions/browser/api/storage/local_value_store_cache.cc
+++ b/extensions/browser/api/storage/local_value_store_cache.cc
@@ -9,6 +9,7 @@
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/files/file_path.h"
+#include "base/metrics/histogram.h"
 #include "content/public/browser/browser_thread.h"
 #include "extensions/browser/api/storage/settings_storage_factory.h"
 #include "extensions/browser/api/storage/settings_storage_quota_enforcer.h"
@@ -91,6 +92,16 @@ ValueStore* LocalValueStoreCache::GetStorage(
       new SettingsStorageQuotaEnforcer(
           quota_, storage_factory_->Create(file_path, extension->id())));
   DCHECK(storage.get());
+
+  if (extension->permissions_data()->HasAPIPermission(
+          APIPermission::kUnlimitedStorage) &&
+      extension->is_hosted_app()) {
+    // We're interested in the amount of space hosted apps are using. Record it
+    // in KB the first time we load the storage for the extension.
+    UMA_HISTOGRAM_COUNTS_100("Extensions.HostedAppUnlimitedStorageUsage",

[Mark P, 2014/09/23 17:12:58]

Are you sure you don't want one of the _MEMORY_ histograms?

[Devlin, 2014/09/23 20:58:03]

Oh, didn't know those existed.  Done.  (To confirm, the histogram now does the
bytes -> KB conversion, right?)

[Mark P, 2014/09/23 22:07:51]

Looking at the code, it appears the answer is yes, it does the conversion for
you.

+                             storage->GetBytesInUse() / 1024);
+  }
+
   storage_map_[extension->id()] = storage;
   return storage.get();
 }