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, 15 insertions, 7 deletions

diff --git a/base/vlog_unittest.cc b/base/vlog_unittest.cc
index ef7247f..3a508f4 100644
--- a/base/vlog_unittest.cc
+++ b/base/vlog_unittest.cc
@@ -16,12 +16,20 @@ namespace {
 
 TEST(VlogTest, NoVmodule) {
   int min_log_level = 0;
-  EXPECT_EQ(0, VlogInfo("", "", &min_log_level).GetVlogLevel("test1"));
-  EXPECT_EQ(0, VlogInfo("0", "", &min_log_level).GetVlogLevel("test2"));
-  EXPECT_EQ(0, VlogInfo("blah", "", &min_log_level).GetVlogLevel("test3"));
-  EXPECT_EQ(0, VlogInfo("0blah1", "", &min_log_level).GetVlogLevel("test4"));
-  EXPECT_EQ(1, VlogInfo("1", "", &min_log_level).GetVlogLevel("test5"));
-  EXPECT_EQ(5, VlogInfo("5", "", &min_log_level).GetVlogLevel("test6"));
+  EXPECT_EQ(0,
+            VlogInfo(std::string(), std::string(), &min_log_level)
+                .GetVlogLevel("test1"));
+  EXPECT_EQ(0,
+            VlogInfo("0", std::string(), &min_log_level).GetVlogLevel("test2"));
+  EXPECT_EQ(
+      0, VlogInfo("blah", std::string(), &min_log_level).GetVlogLevel("test3"));
+  EXPECT_EQ(
+      0,
+      VlogInfo("0blah1", std::string(), &min_log_level).GetVlogLevel("test4"));
+  EXPECT_EQ(1,
+            VlogInfo("1", std::string(), &min_log_level).GetVlogLevel("test5"));
+  EXPECT_EQ(5,
+            VlogInfo("5", std::string(), &min_log_level).GetVlogLevel("test6"));
 }
 
 TEST(VlogTest, MatchVlogPattern) {
@@ -92,7 +100,7 @@ TEST(VlogTest, VmoduleDirs) {
   const char kVModuleSwitch[] =
       "foo/bar.cc=1,baz\\*\\qux.cc=2,*quux/*=3,*/*-inl.h=4";
   int min_log_level = 0;
-  VlogInfo vlog_info("", kVModuleSwitch, &min_log_level);
+  VlogInfo vlog_info(std::string(), kVModuleSwitch, &min_log_level);
   EXPECT_EQ(0, vlog_info.GetVlogLevel("/foo/bar.cc"));
   EXPECT_EQ(0, vlog_info.GetVlogLevel("bar.cc"));
   EXPECT_EQ(1, vlog_info.GetVlogLevel("foo/bar.cc"));