Add histograms to track localStorage size and load time by size.

webkit/dom_storage/dom_storage_cached_area.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "webkit/dom_storage/dom_storage_cached_area.h"
 
 #include "base/basictypes.h"
 #include "base/time.h"
 #include "base/metrics/histogram.h"
 #include "webkit/dom_storage/dom_storage_map.h"
@@ skipping 136 matching lines @@
   // to be ignored.
 
   // Ignore all mutations until OnLoadComplete time.
   ignore_all_mutations_ = true;
   ValuesMap values;
   base::TimeTicks before = base::TimeTicks::Now();
   proxy_->LoadArea(
       connection_id, &values,
       base::Bind(&DomStorageCachedArea::OnLoadComplete,
                  weak_factory_.GetWeakPtr()));
+  base::TimeDelta time_to_prime = base::TimeTicks::Now() - before;
+  // Keeping this histogram named the same (without the ForRenderer suffix)
+  // to maintain histogram continuity.
   UMA_HISTOGRAM_TIMES("LocalStorage.TimeToPrimeLocalStorage",
-                      base::TimeTicks::Now() - before);
+                      time_to_prime);
   map_ = new DomStorageMap(dom_storage::kPerAreaQuota);
   map_->SwapValues(&values);
+
+  size_t local_storage_size_kb = map_->bytes_used() / 1024;
+  // Track localStorage size, from 0-6MB. Note that the maximum size should be
+  // 5MB, but we add some slop since we want to make sure the max size is always
+  // above what we see in practice, since histograms can't change.
+  UMA_HISTOGRAM_CUSTOM_COUNTS("LocalStorage.RendererLocalStorageSizeInKB",
+                              local_storage_size_kb,
+                              0, 6 * 1024, 50);
+  if (local_storage_size_kb < 100) {
+    UMA_HISTOGRAM_TIMES(
+        "LocalStorage.RendererTimeToPrimeLocalStorageUnder100KB",
+        time_to_prime);
+  } else if (local_storage_size_kb < 1000) {
+    UMA_HISTOGRAM_TIMES(
+        "LocalStorage.RendererTimeToPrimeLocalStorage100KBTo1MB",
+        time_to_prime);
+  } else {
+    UMA_HISTOGRAM_TIMES(
+        "LocalStorage.RendererTimeToPrimeLocalStorage1MBTo5MB",
+        time_to_prime);
+  }
 }
 
 void DomStorageCachedArea::Reset() {
   map_ = NULL;
   weak_factory_.InvalidateWeakPtrs();
   ignore_key_mutations_.clear();
   ignore_all_mutations_ = false;
 }
 
 void DomStorageCachedArea::OnLoadComplete(bool success) {
@@ skipping 23 matching lines @@
     ignore_key_mutations_.erase(found);
 }
 
 void DomStorageCachedArea::OnClearComplete(bool success) {
   DCHECK(success);
   DCHECK(ignore_all_mutations_);
   ignore_all_mutations_ = false;
 }
 
 }  // namespace dom_storage