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

9 files changed, 15 insertions, 17 deletions

diff --git a/webkit/fileapi/copy_or_move_file_validator_unittest.cc b/webkit/fileapi/copy_or_move_file_validator_unittest.cc
index 7abc628..6aafa88 100644
--- a/webkit/fileapi/copy_or_move_file_validator_unittest.cc
+++ b/webkit/fileapi/copy_or_move_file_validator_unittest.cc
@@ -58,8 +58,7 @@ class CopyOrMoveFileValidatorTestHelper {
       FileSystemMountPointProvider* mount_point_provider =
           file_system_context_->GetMountPointProvider(src_type_);
       mount_point_provider->GetFileSystemRootPathOnFileThread(
-          SourceURL(""),
-          true /* create */);
+          SourceURL(std::string()), true /* create */);
     }
     DCHECK_EQ(kFileSystemTypeNativeMedia, dest_type_);
     base::FilePath dest_path = base_dir.Append(FILE_PATH_LITERAL("dest_media"));
diff --git a/webkit/fileapi/external_mount_points_unittest.cc b/webkit/fileapi/external_mount_points_unittest.cc
index 4b2ce6cb..8c012fa 100644
--- a/webkit/fileapi/external_mount_points_unittest.cc
+++ b/webkit/fileapi/external_mount_points_unittest.cc
@@ -154,7 +154,7 @@ TEST(ExternalMountPointsTest, GetVirtualPath) {
   // A mount point with an empty path.
   mount_points->RegisterFileSystem("empty_path",
                                    fileapi::kFileSystemTypeNativeLocal,
-                                   base::FilePath(FPL("")));
+                                   base::FilePath(FPL(std::string())));
 
   struct TestCase {
     const base::FilePath::CharType* const local_path;
@@ -271,7 +271,7 @@ TEST(ExternalMountPointsTest, CreateCrackedFileSystemURL) {
                                    base::FilePath(DRIVE FPL("/a/b/c(1)")));
   mount_points->RegisterFileSystem("empty_path",
                                    fileapi::kFileSystemTypeSyncable,
-                                   base::FilePath(FPL("")));
+                                   base::FilePath(FPL(std::string())));
   mount_points->RegisterFileSystem("mount",
                                    fileapi::kFileSystemTypeDrive,
                                    base::FilePath(DRIVE FPL("/root")));
@@ -382,7 +382,7 @@ TEST(ExternalMountPointsTest, CrackVirtualPath) {
                                    base::FilePath(DRIVE FPL("/a/b/c(1)")));
   mount_points->RegisterFileSystem("empty_path",
                                    fileapi::kFileSystemTypeSyncable,
-                                   base::FilePath(FPL("")));
+                                   base::FilePath(FPL(std::string())));
   mount_points->RegisterFileSystem("mount",
                                    fileapi::kFileSystemTypeDrive,
                                    base::FilePath(DRIVE FPL("/root")));
diff --git a/webkit/fileapi/file_system_directory_database_unittest.cc b/webkit/fileapi/file_system_directory_database_unittest.cc
index b612669..5a4b889 100644
--- a/webkit/fileapi/file_system_directory_database_unittest.cc
+++ b/webkit/fileapi/file_system_directory_database_unittest.cc
@@ -569,7 +569,7 @@ TEST_F(FileSystemDirectoryDatabaseTest, TestConsistencyCheck_OrphanFile) {
 
 TEST_F(FileSystemDirectoryDatabaseTest, TestConsistencyCheck_RootLoop) {
   EXPECT_TRUE(db()->IsFileSystemConsistent());
-  MakeHierarchyLink(0, 0, FPL(""));
+  MakeHierarchyLink(0, 0, FPL(std::string()));
   EXPECT_FALSE(db()->IsFileSystemConsistent());
 }
 
diff --git a/webkit/fileapi/file_system_origin_database.cc b/webkit/fileapi/file_system_origin_database.cc
index 1026418..a7405d9 100644
--- a/webkit/fileapi/file_system_origin_database.cc
+++ b/webkit/fileapi/file_system_origin_database.cc
@@ -265,7 +265,7 @@ bool FileSystemOriginDatabase::ListAllOrigins(
     return false;
   DCHECK(origins);
   scoped_ptr<leveldb::Iterator> iter(db_->NewIterator(leveldb::ReadOptions()));
-  std::string origin_key_prefix = OriginToOriginKey("");
+  std::string origin_key_prefix = OriginToOriginKey(std::string());
   iter->Seek(origin_key_prefix);
   origins->clear();
   while (iter->Valid() &&
diff --git a/webkit/fileapi/file_system_util_unittest.cc b/webkit/fileapi/file_system_util_unittest.cc
index 7c946cc..74fc764 100644
--- a/webkit/fileapi/file_system_util_unittest.cc
+++ b/webkit/fileapi/file_system_util_unittest.cc
@@ -115,7 +115,7 @@ TEST_F(FileSystemUtilTest, GetNormalizedFilePath) {
 TEST_F(FileSystemUtilTest, IsAbsolutePath) {
   EXPECT_TRUE(VirtualPath::IsAbsolute(FILE_PATH_LITERAL("/")));
   EXPECT_TRUE(VirtualPath::IsAbsolute(FILE_PATH_LITERAL("/foo/bar")));
-  EXPECT_FALSE(VirtualPath::IsAbsolute(FILE_PATH_LITERAL("")));
+  EXPECT_FALSE(VirtualPath::IsAbsolute(FILE_PATH_LITERAL(std::string())));
   EXPECT_FALSE(VirtualPath::IsAbsolute(FILE_PATH_LITERAL("foo/bar")));
 }
 
diff --git a/webkit/fileapi/local_file_stream_writer_unittest.cc b/webkit/fileapi/local_file_stream_writer_unittest.cc
index d67a7da..41c547e 100644
--- a/webkit/fileapi/local_file_stream_writer_unittest.cc
+++ b/webkit/fileapi/local_file_stream_writer_unittest.cc
@@ -77,7 +77,7 @@ void NeverCalled(int unused) {
 }  // namespace
 
 TEST_F(LocalFileStreamWriterTest, Write) {
-  base::FilePath path = CreateFileWithContent("file_a", "");
+  base::FilePath path = CreateFileWithContent("file_a", std::string());
   scoped_ptr<LocalFileStreamWriter> writer(new LocalFileStreamWriter(path, 0));
   EXPECT_EQ(net::OK, WriteStringToWriter(writer.get(), "foo"));
   EXPECT_EQ(net::OK, WriteStringToWriter(writer.get(), "bar"));
@@ -126,7 +126,7 @@ TEST_F(LocalFileStreamWriterTest, CancelBeforeOperation) {
 }
 
 TEST_F(LocalFileStreamWriterTest, CancelAfterFinishedOperation) {
-  base::FilePath path = CreateFileWithContent("file_a", "");
+  base::FilePath path = CreateFileWithContent("file_a", std::string());
   scoped_ptr<LocalFileStreamWriter> writer(new LocalFileStreamWriter(path, 0));
   EXPECT_EQ(net::OK, WriteStringToWriter(writer.get(), "foo"));
 
diff --git a/webkit/fileapi/local_file_system_cross_operation_unittest.cc b/webkit/fileapi/local_file_system_cross_operation_unittest.cc
index 2929b93..5466069 100644
--- a/webkit/fileapi/local_file_system_cross_operation_unittest.cc
+++ b/webkit/fileapi/local_file_system_cross_operation_unittest.cc
@@ -71,13 +71,11 @@ class CrossOperationTestHelper {
     FileSystemMountPointProvider* mount_point_provider =
         file_system_context_->GetMountPointProvider(src_type_);
     mount_point_provider->GetFileSystemRootPathOnFileThread(
-        SourceURL(""),
-        true /* create */);
+        SourceURL(std::string()), true /* create */);
     mount_point_provider =
         file_system_context_->GetMountPointProvider(dest_type_);
     mount_point_provider->GetFileSystemRootPathOnFileThread(
-        DestURL(""),
-        true /* create */);
+        DestURL(std::string()), true /* create */);
 
     // Grant relatively big quota initially.
     quota_manager_->SetQuota(origin_,
diff --git a/webkit/fileapi/obfuscated_file_util_unittest.cc b/webkit/fileapi/obfuscated_file_util_unittest.cc
index 387f28e..6a6d4a6 100644
--- a/webkit/fileapi/obfuscated_file_util_unittest.cc
+++ b/webkit/fileapi/obfuscated_file_util_unittest.cc
@@ -941,7 +941,7 @@ TEST_F(ObfuscatedFileUtilTest, TestDirectoryOps) {
   EXPECT_EQ(base::PLATFORM_FILE_ERROR_NOT_FOUND,
       ofu()->DeleteDirectory(context.get(), url));
 
-  FileSystemURL root = CreateURLFromUTF8("");
+  FileSystemURL root = CreateURLFromUTF8(std::string());
   EXPECT_FALSE(DirectoryExists(url));
   EXPECT_FALSE(PathExists(url));
   context.reset(NewContext(NULL));
@@ -1081,7 +1081,7 @@ TEST_F(ObfuscatedFileUtilTest, TestReadDirectory) {
 }
 
 TEST_F(ObfuscatedFileUtilTest, TestReadRootWithSlash) {
-  TestReadDirectoryHelper(CreateURLFromUTF8(""));
+  TestReadDirectoryHelper(CreateURLFromUTF8(std::string()));
 }
 
 TEST_F(ObfuscatedFileUtilTest, TestReadRootWithEmptyString) {
diff --git a/webkit/fileapi/syncable/canned_syncable_file_system.cc b/webkit/fileapi/syncable/canned_syncable_file_system.cc
index 954d6a5..f323a1a 100644
--- a/webkit/fileapi/syncable/canned_syncable_file_system.cc
+++ b/webkit/fileapi/syncable/canned_syncable_file_system.cc
@@ -445,7 +445,8 @@ void CannedSyncableFileSystem::ClearChangeForURLInTracker(
 }
 
 FileSystemOperation* CannedSyncableFileSystem::NewOperation() {
-  return file_system_context_->CreateFileSystemOperation(URL(""), NULL);
+  return file_system_context_->CreateFileSystemOperation(URL(std::string()),
+                                                         NULL);
 }
 
 void CannedSyncableFileSystem::OnSyncEnabled(const FileSystemURL& url) {