Rewrite std::string("") to std::string(), Linux edition.

This patch was generated by running the empty_string clang tool
across the Chromium Linux compilation database. Implicitly or
explicitly constructing std::string() with a "" argument is
inefficient as the caller needs to emit extra instructions to
pass an argument, and the constructor needlessly copies a byte
into internal storage. Rewriting these instances to simply call
the default constructor appears to save ~14-18 kilobytes on an
optimized release build.

BUG=none

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=193020

Review URL: https://codereview.chromium.org/13145003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@193040 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 2 insertions, 2 deletions

diff --git a/chrome/browser/metrics/metrics_service.cc b/chrome/browser/metrics/metrics_service.cc
index e68d7bf..c25c8e6 100644
--- a/chrome/browser/metrics/metrics_service.cc
+++ b/chrome/browser/metrics/metrics_service.cc
@@ -391,13 +391,13 @@ class MetricsMemoryDetails : public MemoryDetails {
 // static
 void MetricsService::RegisterPrefs(PrefRegistrySimple* registry) {
   DCHECK(IsSingleThreaded());
-  registry->RegisterStringPref(prefs::kMetricsClientID, "");
+  registry->RegisterStringPref(prefs::kMetricsClientID, std::string());
   registry->RegisterIntegerPref(prefs::kMetricsLowEntropySource,
                                 kLowEntropySourceNotSet);
   registry->RegisterInt64Pref(prefs::kMetricsClientIDTimestamp, 0);
   registry->RegisterInt64Pref(prefs::kStabilityLaunchTimeSec, 0);
   registry->RegisterInt64Pref(prefs::kStabilityLastTimestampSec, 0);
-  registry->RegisterStringPref(prefs::kStabilityStatsVersion, "");
+  registry->RegisterStringPref(prefs::kStabilityStatsVersion, std::string());
   registry->RegisterInt64Pref(prefs::kStabilityStatsBuildTime, 0);
   registry->RegisterBooleanPref(prefs::kStabilityExitedCleanly, true);
   registry->RegisterBooleanPref(prefs::kStabilitySessionEndCompleted, true);