[Tracing] Add metadata filter

chrome/common/trace_event_args_whitelist.cc

 // Copyright 2015 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 "chrome/common/trace_event_args_whitelist.h"
 
 #include "base/bind.h"
 #include "base/strings/pattern.h"
 #include "base/strings/string_tokenizer.h"
 #include "base/strings/string_util.h"
 
 namespace {
 
 struct WhitelistEntry {
   const char* category_name;
   const char* event_name;
   const char* const* arg_name_filter;
 };
 
 const char* const kInputLatencyAllowedArgs[] = {"data", nullptr};
 
 const WhitelistEntry kEventArgsWhitelist[] = {
     {"__metadata", "thread_name", nullptr},
     {"ipc", "ChannelProxy::Context::OnDispatchMessage", nullptr},
     {"ipc", "SyncChannel::Send", nullptr},
     {"toplevel", "*", nullptr},
     {"latencyInfo", "*", kInputLatencyAllowedArgs},
     {nullptr, nullptr, nullptr}};
 
+const char* kMetadataWhitelist[] = {
+  "command_line",
+  "cpu-*",
+  "field-trials",
+  "gpu-*",
+  "highres-ticks",
+  "network-type",
+  "num-cpus",
+  "os-*",
+  "physical-memory",
+  "product-version",
+  "user-agent"
+};
+
 }  // namespace
 
 bool IsTraceArgumentNameWhitelisted(const char* const* granular_filter,
                                     const char* arg_name) {
   for (int i = 0; granular_filter[i] != nullptr; ++i) {
     if (base::MatchPattern(arg_name, granular_filter[i]))
       return true;
   }
 
   return false;
@@ skipping 20 matching lines @@
           *arg_name_filter = base::Bind(&IsTraceArgumentNameWhitelisted,
                                         whitelist_entry.arg_name_filter);
         }
         return true;
       }
     }
   }
 
   return false;
 }
+
+bool IsMetadataWhitelisted(const std::string& metadata_name) {
+  for (auto key : kMetadataWhitelist) {
+    if (base::MatchPattern(metadata_name, key)) {
+      return true;
+    }
+  }
+  return false;
+}