fix crash in window.open in some cases
fix crash on start in WebStorm

this is happening when there is no window context
See https://youtrack.jetbrains.com/issue/WEB-14378

Conflicts:
	Source/bindings/core/v8/V8Binding.cpp
fix previous commit: crash on start in WebStorm
Add lost guard of processingUserGesture

And change to default of processingUserGesture as fail safe
Fix rogerwang/blink#10

test case: http://jsfiddle.net/0104bhnc/1/
supporting more cases of simulating user gesture

Conflicts:
	Source/core/dom/FullscreenElementStack.cpp
	Source/core/html/HTMLMediaElement.cpp