[Tizen][Web] Update WebView terminate crash

[Tizen][Web] Update WebView terminate crash

Due to tizen_7.0 branch will not merge devel/master,
we should sync latest code style by our hands.

== This git commit is squash of below two patches ==

Revert "[Tizen][Web] Fix WebView terminate crash"

This reverts commit 52e86addc31a0b4393e8b7450e4b3c8a877f633d.

[Web] Fix WebView terminate crash

Due to the web context closed before all webview released,
mPlugin and mDestroyWebEnginePtr are invalid.

This patch make reference count so we can assume that
plugin is alive

Change-Id: Ia4a7f810c7aa02c3bd93c061ddb876debd6d4ad5