API functions returning Promises should not throw exceptions.

Source/bindings/core/v8/V8Binding.h

 /*
 * Copyright (C) 2009 Google Inc. All rights reserved.
 * Copyright (C) 2012 Ericsson AB. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
@@ skipping 932 matching lines @@
 
 private:
     v8::HandleScope m_handleScope;
     v8::Context::Scope m_contextScope;
     RefPtr<ScriptState> m_scriptState;
 };
 
 void GetDevToolsFunctionInfo(v8::Handle<v8::Function>, v8::Isolate*, int& scriptId, String& resourceName, int& lineNumber);
 PassRefPtr<TraceEvent::ConvertableToTraceFormat> devToolsTraceEventData(ExecutionContext*, v8::Handle<v8::Function>, v8::Isolate*);
 
 class V8RethrowTryCatchScope FINAL {

[haraken, 2014/07/31 07:54:47]

Just to confirm: Do you have a plan to remove V8RethrowTryCatchScope once the
nested try-catch issue is fixed?

It's confusing to have V8RethrowTryCatchScope, cancel, etc.

[Jens Widell, 2014/07/31 08:29:09]

V8RethrowTryCatchScope isn't a workaround for the nested try-catch problem; it's
a more convenient way to call ReThrow() before returning. I don't see that we
have a reason to remove it, really.

[haraken, 2014/07/31 08:40:29]

Understood. Then it makes sense to have a cancel() method on
V8RethrowTryCatchScope.

 public:
-    explicit V8RethrowTryCatchScope(v8::TryCatch& block) : m_block(block) { }
+    explicit V8RethrowTryCatchScope(v8::TryCatch& block) : m_block(block), m_isCanceled(false) { }

[haraken, 2014/07/31 07:54:47]

Drop explicit.

[yhirano, 2014/08/01 02:27:57]

It should be explicit, shouldn't it?

[haraken, 2014/08/01 02:42:40]

Sorry, I misread the code.

+    void cancel() { m_isCanceled = true; }
     ~V8RethrowTryCatchScope()
     {
-        // ReThrow() is a no-op if no exception has been caught, so always call.
-        m_block.ReThrow();
+        if (!m_isCanceled) {
+            // ReThrow() is a no-op if no exception has been caught, so always
+            // call.
+            m_block.ReThrow();
+        }
     }
 
 private:
     v8::TryCatch& m_block;
-};
-
-class V8ResetTryCatchScope FINAL {
-public:
-    explicit V8ResetTryCatchScope(v8::TryCatch& block) : m_block(block) { }
-    ~V8ResetTryCatchScope()
-    {
-        m_block.Reset();
-    }
-
-private:
-    v8::TryCatch& m_block;
+    bool m_isCanceled;
 };
 
 } // namespace blink
 
 #endif // V8Binding_h