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

3 files changed, 6 insertions, 6 deletions

diff --git a/sync/internal_api/public/base/model_type_invalidation_map_unittest.cc b/sync/internal_api/public/base/model_type_invalidation_map_unittest.cc
index f051479..772ee7e 100644
--- a/sync/internal_api/public/base/model_type_invalidation_map_unittest.cc
+++ b/sync/internal_api/public/base/model_type_invalidation_map_unittest.cc
@@ -35,7 +35,7 @@ TEST_F(ModelTypeInvalidationMapTest, TypeInvalidationMapToValue) {
   scoped_ptr<DictionaryValue> value(ModelTypeInvalidationMapToValue(states));
   EXPECT_EQ(2u, value->size());
   ExpectDictStringValue(states[BOOKMARKS].payload, *value, "Bookmarks");
-  ExpectDictStringValue("", *value, "Apps");
+  ExpectDictStringValue(std::string(), *value, "Apps");
   EXPECT_FALSE(value->HasKey("Preferences"));
 }
 
diff --git a/sync/internal_api/public/base/ordinal_unittest.cc b/sync/internal_api/public/base/ordinal_unittest.cc
index 20a6d19..8c77d6d 100644
--- a/sync/internal_api/public/base/ordinal_unittest.cc
+++ b/sync/internal_api/public/base/ordinal_unittest.cc
@@ -87,7 +87,7 @@ COMPILE_ASSERT(LargeOrdinal::kRadix == 256,
 // IsValid() should return false for all of them.
 TEST(Ordinal, Invalid) {
   // Length criterion.
-  EXPECT_FALSE(TestOrdinal("").IsValid());
+  EXPECT_FALSE(TestOrdinal(std::string()).IsValid());
   EXPECT_FALSE(LongOrdinal("0001").IsValid());
 
   const char kBeforeZero[] = { '0' - 1, '\0' };
diff --git a/sync/internal_api/public/base/unique_position.cc b/sync/internal_api/public/base/unique_position.cc
index a47d42b..b6c18ef 100644
--- a/sync/internal_api/public/base/unique_position.cc
+++ b/sync/internal_api/public/base/unique_position.cc
@@ -61,7 +61,7 @@ UniquePosition UniquePosition::FromInt64(
 UniquePosition UniquePosition::InitialPosition(
     const std::string& suffix) {
   DCHECK(IsValidSuffix(suffix));
-  return UniquePosition("", suffix);
+  return UniquePosition(std::string(), suffix);
 }
 
 // static.
@@ -175,7 +175,7 @@ std::string UniquePosition::FindSmallerWithSuffix(
 
   if (suffix_zeroes > ref_zeroes) {
     // Implies suffix < ref.
-    return "";
+    return std::string();
   }
 
   if (suffix.substr(suffix_zeroes) < reference.substr(ref_zeroes)) {
@@ -210,7 +210,7 @@ std::string UniquePosition::FindGreaterWithSuffix(
 
   if (suffix_FFs > ref_FFs) {
     // Implies suffix > reference.
-    return "";
+    return std::string();
   }
 
   if (suffix.substr(suffix_FFs) > reference.substr(ref_FFs)) {
@@ -244,7 +244,7 @@ std::string UniquePosition::FindBetweenWithSuffix(
 
   // Sometimes our suffix puts us where we want to be.
   if (before < suffix && suffix < after) {
-    return "";
+    return std::string();
   }
 
   size_t i = 0;