API functions returning Promises should not throw exceptions.

Source/bindings/tests/idls/TestObject.idl

Index: Source/bindings/tests/idls/TestObject.idl
diff --git a/Source/bindings/tests/idls/TestObject.idl b/Source/bindings/tests/idls/TestObject.idl
index bbe9ff6e46072102dbd510a599645157107d654a..00994e9895c392112c2f20e6dc35813c9a7d3f62 100644
--- a/Source/bindings/tests/idls/TestObject.idl
+++ b/Source/bindings/tests/idls/TestObject.idl
@@ -366,7 +366,8 @@ interface TestObject {
     // Exceptional types
     Dictionary dictionaryMethod();
     NodeFilter nodeFilterMethod();
-    Promise promiseMethod();
+    Promise promiseMethod(long arg1, Dictionary arg2, DOMString arg3, DOMString... variadic);

[bashi, 2014/07/31 02:02:24]

Is it possible to use enums instead of Dictionary for arg2? I'm planning to
remove Dictionary from IDL files so it would be good if we can avoid adding
Dictionary.

[yhirano, 2014/07/31 03:38:03]

Can you tell me your plan?
I added Dictionary test case because Dictionary is specially handled.
Will the Dictionary specific code be deleted?
Will another non-general code be added?

[bashi, 2014/07/31 04:38:42]

In my plan, Dictionary will be replaced by specific IDL dictionaries. Here is an
example:
https://codereview.chromium.org/429853002/diff/20001/Source/core/css/FontFace...
https://codereview.chromium.org/429853002/diff/20001/Source/core/css/FontFace...
Yes. It seems that enums are also handled in a similar way in
generate_argument() macro in method.cpp template, so I thought we may be able to
use enums instead.
"Dictionary" class specific code should be gone, but we will treat IDL
dictionaries(of which idl_type.is_dictionary is True) in a similar way of
"Dictionary" if necessary.

Anyway, I'm totally fine using Dictionary here if it's suitable for your
purpose.

[yhirano, 2014/08/01 03:52:54]

Thank you.
Let me leave it be to keep the test coverage.

+    Promise promiseMethodWithoutExceptionState(Dictionary arg1);
     SerializedScriptValue serializedScriptValueMethod();
     XPathNSResolver xPathNSResolverMethod();
     void voidMethodDictionaryArg(Dictionary dictionaryArg);