Revert of WebAudio: Remove AudioNode::RefType.

Revert of WebAudio: Remove AudioNode::RefType. (https://codereview.chromium.org/349213007/)

Reason for revert:
Made webaudio/delaynode-max-nondefault-delay.html flaky.


Original issue's description:
> WebAudio: Remove AudioNode::RefType.
> 
> The motivation of this CL is to reduce manual ref()/deref().
> 
> AudioNode has two types of ref()/deref(); RefTypeNormal and RefTypeConnection.
> It made the code complex, and we couldn't use RefPtr<> for the connection type
> references.
> 
> This CL removes AudioNode::RefType.
>  - m_normalRefCount and m_connectionRefCount were updated independently. After
>    this CL, connection type references updates both of them.
>  - We use RefPtr<> for connection type references, and call
>    AudioNode::makeConnection() and AudioNode::breakConnection() explicitly when
>    connections are updated.
> 
> BUG=392788
> TEST=none; This CL should not have behavior changes.
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=177910

NOTRY=true
TBR=rtoy@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=177916

[tkent, 2014-07-11 08:56:34]

Created Revert of WebAudio: Remove AudioNode::RefType.

[haraken, 2014-07-11 08:56:51]

LGTM

[commit-bot: I haz the power, 2014-07-11 08:57:09]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/tkent@chromium.org/385953003/1

[commit-bot: I haz the power, 2014-07-11 08:57:45]

Change committed as 177916