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

2 files changed, 8 insertions, 8 deletions

diff --git a/device/bluetooth/bluetooth_utils.cc b/device/bluetooth/bluetooth_utils.cc
index 1e7b827..4f30202 100644
--- a/device/bluetooth/bluetooth_utils.cc
+++ b/device/bluetooth/bluetooth_utils.cc
@@ -21,18 +21,18 @@ namespace bluetooth_utils {
 
 std::string CanonicalUuid(std::string uuid) {
   if (uuid.empty())
-    return "";
+    return std::string();
 
   if (uuid.size() < 11 && uuid.find("0x") == 0)
     uuid = uuid.substr(2);
 
   if (!(uuid.size() == 4 || uuid.size() == 8 || uuid.size() == 36))
-    return "";
+    return std::string();
 
   if (uuid.size() == 4 || uuid.size() == 8) {
     for (size_t i = 0; i < uuid.size(); ++i) {
       if (!IsHexDigit(uuid[i]))
-        return "";
+        return std::string();
     }
 
     if (uuid.size() == 4)
@@ -45,10 +45,10 @@ std::string CanonicalUuid(std::string uuid) {
   for (int i = 0; i < kUuidSize; ++i) {
     if (i == 8 || i == 13 || i == 18 || i == 23) {
       if (uuid[i] != '-')
-        return "";
+        return std::string();
     } else {
       if (!IsHexDigit(uuid[i]))
-        return "";
+        return std::string();
       uuid_result[i] = tolower(uuid[i]);
     }
   }
diff --git a/device/media_transfer_protocol/media_transfer_protocol_manager.cc b/device/media_transfer_protocol/media_transfer_protocol_manager.cc
index bbd13b3..d3fce03 100644
--- a/device/media_transfer_protocol/media_transfer_protocol_manager.cc
+++ b/device/media_transfer_protocol/media_transfer_protocol_manager.cc
@@ -111,7 +111,7 @@ class MediaTransferProtocolManagerImpl : public MediaTransferProtocolManager {
                            const OpenStorageCallback& callback) OVERRIDE {
     DCHECK(thread_checker_.CalledOnValidThread());
     if (!ContainsKey(storage_info_map_, storage_name)) {
-      callback.Run("", true);
+      callback.Run(std::string(), true);
       return;
     }
     open_storage_callbacks_.push(callback);
@@ -333,13 +333,13 @@ class MediaTransferProtocolManagerImpl : public MediaTransferProtocolManager {
       open_storage_callbacks_.front().Run(handle, false);
     } else {
       NOTREACHED();
-      open_storage_callbacks_.front().Run("", true);
+      open_storage_callbacks_.front().Run(std::string(), true);
     }
     open_storage_callbacks_.pop();
   }
 
   void OnOpenStorageError() {
-    open_storage_callbacks_.front().Run("", true);
+    open_storage_callbacks_.front().Run(std::string(), true);
     open_storage_callbacks_.pop();
   }