Undo a rename of dbus::Message::GetSignature.

dbus::Message::GetSignature() was incorrectly renamed to
dbus::Message::GetDataSigature() in
https://codereview.chromium.org/502793002. This CL undoes that.

BUG=None
TEST=dbus_unittests

Review URL: https://codereview.chromium.org/494263003

Cr-Commit-Position: refs/heads/master@{#291660}

dbus/message.cc

@@ -262,7 +262,7 @@ std::string Message::ToString() {
   AppendStringHeader("member", GetMember(), &headers);
   AppendStringHeader("error_name", GetErrorName(), &headers);
   AppendStringHeader("sender", GetSender(), &headers);
-  AppendStringHeader("signature", GetDataSignature(), &headers);
+  AppendStringHeader("signature", GetSignature(), &headers);
   AppendUint32Header("serial", GetSerial(), &headers);
   AppendUint32Header("reply_serial", GetReplySerial(), &headers);
 
@@ -333,7 +333,7 @@ std::string Message::GetSender() {
   return sender ? sender : "";
 }
 
-std::string Message::GetDataSignature() {
+std::string Message::GetSignature() {
   const char* signature = dbus_message_get_signature(raw_message_);
   return signature ? signature : "";
 }

dbus/message.h

@@ -111,7 +111,7 @@ class CHROME_DBUS_EXPORT Message {
   std::string GetMember();
   std::string GetErrorName();
   std::string GetSender();
-  std::string GetDataSignature();
+  std::string GetSignature();
   // Gets the serial and reply serial numbers. Returns 0 if not set.
   uint32 GetSerial();
   uint32 GetReplySerial();