Deal with unhandled exceptions the same way in all Dart api functions.

runtime/bin/process_script.cc

 // Copyright (c) 2011, 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.
 
 // Handle dart scripts.
 
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
 
@@ skipping 80 matching lines @@
                                            Dart_Handle url,
                                            bool import_builtin_lib) {
   if (!Dart_IsLibrary(library)) {
     return Dart_Error("not a library");
   }
   if (!Dart_IsString8(url)) {
     return Dart_Error("url is not a string");
   }
   const char* url_chars = NULL;
   Dart_Handle result = Dart_StringToCString(url, &url_chars);
-  if (!Dart_IsValid(result)) {
+  if (Dart_IsError(result)) {
     return Dart_Error("accessing url characters failed");
   }
 
   if (tag == kCanonicalizeUrl) {
     // Create the full path based on the including library and the current url.
 
     // Get the url of the calling library.
     Dart_Handle library_url = Dart_LibraryUrl(library);
-    if (!Dart_IsValid(library_url)) {
+    if (Dart_IsError(library_url)) {
       return Dart_Error("accessing library url failed");
     }
     if (!Dart_IsString8(library_url)) {
       return Dart_Error("library url is not a string");
     }
     const char* library_url_chars = NULL;
     result = Dart_StringToCString(library_url, &library_url_chars);
-    if (!Dart_IsValid(result)) {
+    if (Dart_IsError(result)) {
       return Dart_Error("accessing library url characters failed");
     }
 
     // Calculate the path.
     const char* canon_url_chars = CanonicalizeUrl(library_url_chars, url_chars);
     Dart_Handle canon_url = Dart_NewString(canon_url_chars);
     free(const_cast<char*>(canon_url_chars));
 
     return canon_url;
   }
 
   // The tag is either an import or a source tag. Read the file based on the
   // url chars.
   Dart_Handle source = ReadStringFromFile(url_chars);
-  if (!Dart_IsValid(source)) {
+  if (Dart_IsError(source)) {
     return source;  // source contains the error string.
   }
   if (tag == kImportTag) {
     Dart_Handle new_lib = Dart_LoadLibrary(url, source);
-    if (import_builtin_lib && Dart_IsValid(new_lib)) {
+    if (import_builtin_lib && !Dart_IsError(new_lib)) {
       Builtin_ImportLibrary(new_lib);
     }
     return new_lib;  // Return library object or an error string.
   } else if (tag == kSourceTag) {
     return Dart_LoadSource(library, url, source);
   }
   return Dart_Error("wrong tag");
 }
 
 static Dart_Handle MainLibraryTagHandler(Dart_LibraryTag tag,
                                          Dart_Handle library,
                                          Dart_Handle url) {
   const bool kImportBuiltinLib = true;  // Import builtin library.
   return LibraryTagHandlerHelper(tag, library, url, kImportBuiltinLib);
 }
 
 
 static Dart_Handle CreateSnapshotLibraryTagHandler(Dart_LibraryTag tag,
                                                    Dart_Handle library,
                                                    Dart_Handle url) {
   const bool kDontImportBuiltinLib = false;  // Do not import builtin lib.
   return LibraryTagHandlerHelper(tag, library, url, kDontImportBuiltinLib);
 }
 
 
 Dart_Handle LoadScript(const char* script_name) {
   Dart_Handle source = ReadStringFromFile(script_name);
-  if (!Dart_IsValid(source)) {
+  if (Dart_IsError(source)) {
     return source;
   }
   Dart_Handle url = Dart_NewString(script_name);
 
   return Dart_LoadScript(url, source, MainLibraryTagHandler);
 }
 
 
 Dart_Handle LoadSnapshotCreationScript(const char* script_name) {
   Dart_Handle source = ReadStringFromFile(script_name);
-  if (!Dart_IsValid(source)) {
+  if (Dart_IsError(source)) {
     return source;
   }
   Dart_Handle url = Dart_NewString(script_name);
 
   return Dart_LoadScript(url, source, CreateSnapshotLibraryTagHandler);
 }