Added a comment for Dart_LoadSource.

runtime/include/dart_api.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef INCLUDE_DART_API_H_
 #define INCLUDE_DART_API_H_
 
 /** \mainpage Dart Embedding API Reference
  *
  * Dart is a class-based programming language for creating structured
@@ skipping 2516 matching lines @@
 // TODO(turnidge): Consider returning Dart_Null() when the library is
 // not found to distinguish that from a true error case.
 
 DART_EXPORT Dart_Handle Dart_LoadLibrary(Dart_Handle url,
                                          Dart_Handle source);
 
 
 DART_EXPORT Dart_Handle Dart_LibraryImportLibrary(Dart_Handle library,
                                                   Dart_Handle import);
 
+/**
+ * Loads a source string into a library.
+ *
+ * \param library A library
+ * \param url A url identifying the origin of the source
+ * \param source A string of Dart source
+ *
+ * \return A valid handle if no error occurs during the operation.
+ */
 DART_EXPORT Dart_Handle Dart_LoadSource(Dart_Handle library,
                                         Dart_Handle url,
                                         Dart_Handle source);
 // TODO(turnidge): Rename to Dart_LibraryLoadSource?
 
 /**
  * Sets the callback used to resolve native functions for a library.
  *
  * \param library A library.
  * \param resolver A native entry resolver.
@@ skipping 11 matching lines @@
 // information that can be used for better profile reports for
 // dynamically generated code.
 DART_EXPORT void Dart_InitPprofSupport();
 DART_EXPORT void Dart_GetPprofSymbolInfo(void** buffer, int* buffer_size);
 
 // Support for generating flow graph compiler debugging output into a file.
 typedef void (*FileWriterFunction)(const char* buffer, int64_t num_bytes);
 DART_EXPORT void Dart_InitFlowGraphPrinting(FileWriterFunction function);
 
 #endif  // INCLUDE_DART_API_H_