[tracing] Add a memory dump provider for DOM storage

content/browser/dom_storage/dom_storage_area.cc

 // Copyright 2013 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 "content/browser/dom_storage/dom_storage_area.h"
 
 #include <algorithm>
+#include <cctype>  // for std::isalnum
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
 #include "base/process/process_info.h"
+#include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/time/time.h"
+#include "base/trace_event/memory_dump_manager.h"
+#include "base/trace_event/process_memory_dump.h"
 #include "content/browser/dom_storage/dom_storage_namespace.h"
 #include "content/browser/dom_storage/dom_storage_task_runner.h"
 #include "content/browser/dom_storage/local_storage_database_adapter.h"
 #include "content/browser/dom_storage/session_storage_database.h"
 #include "content/browser/dom_storage/session_storage_database_adapter.h"
 #include "content/common/dom_storage/dom_storage_map.h"
 #include "content/common/dom_storage/dom_storage_types.h"
 #include "content/public/browser/browser_thread.h"
 #include "storage/browser/database/database_util.h"
 #include "storage/common/database/database_identifier.h"
@@ skipping 297 matching lines @@
   if (!backing_)
     return;
 
   bool success = task_runner_->PostShutdownBlockingTask(
       FROM_HERE,
       DOMStorageTaskRunner::COMMIT_SEQUENCE,
       base::Bind(&DOMStorageArea::ShutdownInCommitSequence, this));
   DCHECK(success);
 }
 
+void DOMStorageArea::OnMemoryDump(base::trace_event::ProcessMemoryDump* pmd) {
+  if (!map_->bytes_used())
+    return;
+  // Limit the url length to 50 and strip special characters.
+  std::string url = origin_.spec().substr(0, 50);
+  for (size_t index = 0; index < url.size(); ++index) {
+    if (!std::isalnum(url[index]))
+      url[index] = '_';

[michaeln, 2016/04/22 23:39:41]

From a privacy perspective, is it ok to capture URLs in these traces? Just
checking.

[ssid, 2016/04/23 00:19:15]

Actually traces contain lot of sensitive information, like memory maps.
We have made sure that the tracing infra is not accessible without the visual
consent of the user. So, no script can start tracing and collect traces.

More over there is already a predecessor for adding urls:
https://chromium.googlesource.com/chromium/src/+blame/master/third_party/WebK...

+  }
+  std::string name = StringPrintf("dom_storage/%s/%p", url.c_str(), this);
+  auto mad = pmd->CreateAllocatorDump(name + "/storage_map");
+  mad->AddScalar(base::trace_event::MemoryAllocatorDump::kNameSize,
+                 base::trace_event::MemoryAllocatorDump::kUnitsBytes,
+                 map_->bytes_used());
+
+  const char* system_allocator_name =
+      base::trace_event::MemoryDumpManager::GetInstance()
+          ->system_allocator_pool_name();
+  if (system_allocator_name)
+    pmd->AddSuballocation(mad->guid(), system_allocator_name);
+  // TODO(ssid): Add memory usage of backing storage crbug.com/605785.
+}
+
 void DOMStorageArea::InitialImportIfNeeded() {
   if (is_initial_import_done_)
     return;
 
   DCHECK(backing_.get());
 
   base::TimeTicks before = base::TimeTicks::Now();
   DOMStorageValuesMap initial_values;
   backing_->ReadAllValues(&initial_values);
   map_->SwapValues(&initial_values);
@@ skipping 132 matching lines @@
         commit_batch_->clear_all_first,
         commit_batch_->changed_values);
     DCHECK(success);
   }
   commit_batch_.reset();
   backing_.reset();
   session_storage_backing_ = NULL;
 }
 
 }  // namespace content