Port more String and HashMap usages

sky/engine/tonic/dart_library_provider.h

Index: sky/engine/tonic/dart_library_provider.h
diff --git a/sky/engine/tonic/dart_library_provider.h b/sky/engine/tonic/dart_library_provider.h
index e849fdc0473ca206ae6e0f6ad5062e1394006288..eef3c659d5dfa1ec9cf10264265564e72c5ea4f8 100644
--- a/sky/engine/tonic/dart_library_provider.h
+++ b/sky/engine/tonic/dart_library_provider.h
@@ -5,10 +5,11 @@
 #ifndef SKY_ENGINE_TONIC_DART_LIBRARY_PROVIDER_H_
 #define SKY_ENGINE_TONIC_DART_LIBRARY_PROVIDER_H_
 
+#include <string>
+
 #include "base/callback.h"
 #include "dart/runtime/include/dart_api.h"
 #include "mojo/public/cpp/system/data_pipe.h"
-#include "sky/engine/wtf/text/WTFString.h"
 
 namespace blink {
 
@@ -17,7 +18,7 @@ typedef base::Callback<void(mojo::ScopedDataPipeConsumerHandle)>
 
 class DartLibraryProvider {
  public:
-  virtual void GetLibraryAsStream(const String& name,
+  virtual void GetLibraryAsStream(const std::string& name,
                                   DataPipeConsumerCallback callback) = 0;
 
   virtual Dart_Handle CanonicalizeURL(Dart_Handle library, Dart_Handle url) = 0;