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

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

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@193020 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 10 insertions, 9 deletions

diff --git a/chrome/test/perf/startup_test.cc b/chrome/test/perf/startup_test.cc
index 1d8243f..0a07ce8 100644
--- a/chrome/test/perf/startup_test.cc
+++ b/chrome/test/perf/startup_test.cc
@@ -295,7 +295,8 @@ class StartupTest : public UIPerfTest {
                           "%.2f,",
                           timings[i].end_to_end.InMillisecondsF());
     }
-    perf_test::PrintResultList(graph, "", trace, times, "ms", important);
+    perf_test::PrintResultList(
+        graph, std::string(), trace, times, "ms", important);
 
     if (num_tabs > 0) {
       std::string name_base = trace;
@@ -305,15 +306,15 @@ class StartupTest : public UIPerfTest {
       name = name_base + "-start";
       for (int i = 0; i < numCycles; ++i)
         base::StringAppendF(&times, "%.2f,", timings[i].first_start_ms);
-      perf_test::PrintResultList(graph, "", name.c_str(), times, "ms",
-                                 important);
+      perf_test::PrintResultList(
+          graph, std::string(), name.c_str(), times, "ms", important);
 
       times.clear();
       name = name_base + "-first";
       for (int i = 0; i < numCycles; ++i)
         base::StringAppendF(&times, "%.2f,", timings[i].first_stop_ms);
-      perf_test::PrintResultList(graph, "", name.c_str(), times, "ms",
-                                 important);
+      perf_test::PrintResultList(
+          graph, std::string(), name.c_str(), times, "ms", important);
 
       if (nth_timed_tab > 0) {
         // Display only the time necessary to load the first n tabs.
@@ -321,8 +322,8 @@ class StartupTest : public UIPerfTest {
         name = name_base + "-" + base::IntToString(nth_timed_tab);
         for (int i = 0; i < numCycles; ++i)
           base::StringAppendF(&times, "%.2f,", timings[i].nth_tab_stop_ms);
-        perf_test::PrintResultList(graph, "", name.c_str(), times, "ms",
-                                   important);
+        perf_test::PrintResultList(
+            graph, std::string(), name.c_str(), times, "ms", important);
       }
 
       if (num_tabs > 1) {
@@ -331,8 +332,8 @@ class StartupTest : public UIPerfTest {
         name = name_base + "-all";
         for (int i = 0; i < numCycles; ++i)
           base::StringAppendF(&times, "%.2f,", timings[i].last_stop_ms);
-        perf_test::PrintResultList(graph, "", name.c_str(), times, "ms",
-                                   important);
+        perf_test::PrintResultList(
+            graph, std::string(), name.c_str(), times, "ms", important);
       }
     }
   }