When persisting UMA logs to disk, cap log size based on both the XML and protocol buffer logs.

chrome/common/metrics/metrics_log_manager.cc

Index: chrome/common/metrics/metrics_log_manager.cc
diff --git a/chrome/common/metrics/metrics_log_manager.cc b/chrome/common/metrics/metrics_log_manager.cc
index e78ce89e152419e09669e77c104c7ab8b9f9ad03..2e1261f3c05f3d0166d940b158add824713383a7 100644
--- a/chrome/common/metrics/metrics_log_manager.cc
+++ b/chrome/common/metrics/metrics_log_manager.cc
@@ -10,6 +10,8 @@
 #include "third_party/bzip2/bzlib.h"
 #endif
 
+#include <algorithm>
+
 #include "base/metrics/histogram.h"
 #include "base/string_util.h"
 #include "chrome/common/metrics/metrics_log_base.h"
@@ -37,6 +39,10 @@ bool MetricsLogManager::SerializedLog::empty() const {
   return xml.empty();
 }
 
+size_t MetricsLogManager::SerializedLog::length() const {
+  return std::max(xml.length(), proto.length());
+}
+
 void MetricsLogManager::SerializedLog::swap(SerializedLog& log) {
   xml.swap(log.xml);
   proto.swap(log.proto);