fix 773b4579a5cefb00c061820315462b8a6be5fe29
Get current RenderView based on Entered context

The extension's function is compiled in the first
window's context. It's needed to get the caller's
context.

Fix #1187
replace webkit ImageDecoder
Fix 1421ea5965c2ec6e0242f73dfed94963a023af9b