bindings: Support sequence in callback function arguments

third_party/WebKit/Source/bindings/templates/callback_function.cpp

Index: third_party/WebKit/Source/bindings/templates/callback_function.cpp
diff --git a/third_party/WebKit/Source/bindings/templates/callback_function.cpp b/third_party/WebKit/Source/bindings/templates/callback_function.cpp
index d0c68a56e4c0349e5fbcb8933605e1dc465bcdca..7ef89e485113eb4acd7bc962b7096d88cdbee1a0 100644
--- a/third_party/WebKit/Source/bindings/templates/callback_function.cpp
+++ b/third_party/WebKit/Source/bindings/templates/callback_function.cpp
@@ -29,7 +29,9 @@ bool {{v8_class}}::call({{argument_declarations | join(', ')}})
 
     if (m_callback.isEmpty())
         return false;
+
     ScriptState::Scope scope(scriptState);
+    ExceptionState exceptionState(scriptState->isolate(), ExceptionState::ExecutionContext, "{{cpp_class}}");

[bashi, 2016/09/21 02:00:21]

Always declare exceptionState for simplicity.

Another option would be passing exceptionState to call(). Maybe this approach is
more reasonable but number of arguments increases. WDYT? I don't have strong
opinion here.

[peria, 2016/09/21 02:21:36]

+1 to declare it here.

[haraken, 2016/09/21 02:25:12]

What is an expected behavior when an exception is thrown to the ExceptionState?

IIUC an expected behavior would be just to suppress the exception (c.f., we have
the v8::TryCatch block at line 47). If that is the case, we'll need to put the
ExceptionState inside the v8::TryCatch block.

[bashi, 2016/09/21 05:01:45]

Hmm, glanced at existing hand-written callbacks and it seems there are three
cases:
1. suppress exceptions (like this template)
2. rethrow exceptions (CustomElementCallback)
3. Don't use TryCatch (IDBObserverCallback)

Maybe the right behavior is:
- Pass ExceptionState
- Use TryCatch inside call()
- ExceptionState::rethrowV8Exception() when V8ScriptRunner::callFunction() fails
- Callers may call ExceptionState::clearException()

?

[Yuki, 2016/09/21 07:59:37]

Yes, I think that's the expected design.
Always killing an exception is wrong.  (But l-g-t-m'ed because I thought it's
okay as the first step.)

In general, I think an owner of this callback function object should be
responsible for everything (e.g. lifetime, exception handling) except for
invoking a callback function.

 
     {% for argument in arguments %}
     v8::Local<v8::Value> {{argument.argument_name}} = {{argument.cpp_value_to_v8_value}};