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, 6 insertions, 4 deletions

diff --git a/chrome/browser/page_cycler/page_cycler.cc b/chrome/browser/page_cycler/page_cycler.cc
index 04086d2..b78e1fe 100644
--- a/chrome/browser/page_cycler/page_cycler.cc
+++ b/chrome/browser/page_cycler/page_cycler.cc
@@ -192,10 +192,12 @@ void PageCycler::PrepareResultsOnBackgroundThread() {
     base::ProcessId pid = base::GetCurrentProcId();
 #endif  // OS_WIN
     ChromeProcessList chrome_processes(GetRunningChromeProcesses(pid));
-    output += perf_test::MemoryUsageInfoToString("", chrome_processes, pid);
-    output += perf_test::IOPerfInfoToString("", chrome_processes, pid);
-    output += perf_test::SystemCommitChargeToString("",
-              base::GetSystemCommitCharge(), false);
+    output += perf_test::MemoryUsageInfoToString(
+        std::string(), chrome_processes, pid);
+    output +=
+        perf_test::IOPerfInfoToString(std::string(), chrome_processes, pid);
+    output += perf_test::SystemCommitChargeToString(
+        std::string(), base::GetSystemCommitCharge(), false);
     output.append("Pages: [" + urls_string_ + "]\n");
     output.append("*RESULT times: t_ref= [" + timings_string_ + "] ms\n");
   }