Fix for issue 23908 - error message reports the exact error when a native extension fails to load.

runtime/bin/main.cc

Index: runtime/bin/main.cc
diff --git a/runtime/bin/main.cc b/runtime/bin/main.cc
index 1429ff4e65315ec2d5760de07f3f8c92ad1eebbc..c23281f67fb05857a3776cf0116ef41175987ff8 100644
--- a/runtime/bin/main.cc
+++ b/runtime/bin/main.cc
@@ -1092,15 +1092,21 @@ static void ReadSnapshotFile(const char* filename,
 
 
 static void* LoadLibrarySymbol(const char* libname, const char* symname) {
-  void* library = Extensions::LoadExtensionLibrary(libname);
-  if (library == NULL) {
-    Log::PrintErr("Error: Failed to load library '%s'\n", libname);
-    exit(kErrorExitCode);
+  void* library = NULL;
+  Dart_Handle result = Extensions::LoadExtensionLibrary(libname, &library);
+  if (Dart_IsError(result)) {
+    ErrorExit(kErrorExitCode,
+              "Error: Failed to load library '%s' - '%s'\n",
+              libname,
+              Dart_GetError(result));
   }
-  void* symbol = Extensions::ResolveSymbol(library, symname);
-  if (symbol == NULL) {
-    Log::PrintErr("Error: Failed to load symbol '%s'\n", symname);
-    exit(kErrorExitCode);
+  void* symbol = NULL;
+  result = Extensions::ResolveSymbol(library, symname, &symbol);
+  if (Dart_IsError(result)) {
+    ErrorExit(kErrorExitCode,
+              "Error: Failed to load symbol '%s' - '%s'\n",
+              symname,
+              Dart_GetError(result));
   }
   return symbol;
 }