Fix debugger crash in Sky

This is actually a backport of the following Blink change https://src.chromium.org/viewvc/blink?view=rev&revision=185426. New scope types introduced by ES6 features are not yes supported by DevTools and should just be ignored by the debugger. ScriptScope that caused troubles in this particular case was supported in V8 debugger quite recently (https://codereview.chromium.org/726643002).

This fixes following crash on pause in Sky:
#0  0x00007f8a39cffe1b in blink::TypeBuilder::Debugger::Scope::Type::assertCorrectValue (value=0xd98ce760450) at gen/sky/core/InspectorTypeBuilder.cpp:596
#1  0x00007f8a39d00072 in blink::TypeBuilder::Debugger::Scope::assertCorrectValue (value=0xd98ce658898) at gen/sky/core/InspectorTypeBuilder.cpp:610
#2  0x00007f8a39d033c5 in blink::TypeBuilder::StructItemTraits::assertCorrectValue<blink::TypeBuilder::Debugger::Scope> (value=0xd98ce658898) at gen/sky/core/InspectorTypeBuilder.h:160
#3  0x00007f8a39d02f71 in blink::TypeBuilder::Array<blink::TypeBuilder::Debugger::Scope>::assertCorrectValue (value=0xd98ce60af00) at gen/sky/core/InspectorTypeBuilder.h:139
#4  0x00007f8a39cffaaf in blink::TypeBuilder::Debugger::CallFrame::assertCorrectValue (value=0xd98ce658420) at gen/sky/core/InspectorTypeBuilder.cpp:569
#5  0x00007f8a3a753435 in blink::TypeBuilder::StructItemTraits::assertCorrectValue<blink::TypeBuilder::Debugger::CallFrame> (value=0xd98ce658420) at gen/sky/core/InspectorTypeBuilder.h:160
#6  0x00007f8a3a753371 in blink::TypeBuilder::Array<blink::TypeBuilder::Debugger::CallFrame>::assertCorrectValue (value=0xd98ce60af50) at gen/sky/core/InspectorTypeBuilder.h:139
#7  0x00007f8a3a752fa6 in blink::TypeBuilder::Array<blink::TypeBuilder::Debugger::CallFrame>::runtimeCast (value=...) at gen/sky/core/InspectorTypeBuilder.h:121
#8  0x00007f8a3a751e8c in blink::InjectedScript::wrapCallFrames (this=0x7f8a5560d988, callFrames=..., asyncOrdinal=0) at ../../sky/engine/core/inspector/InjectedScript.cpp:261
#9  0x00007f8a3a765350 in blink::InspectorDebuggerAgent::currentCallFrames (this=0xd98ce689410) at ../../sky/engine/core/inspector/InspectorDebuggerAgent.cpp:1149
#10 0x00007f8a3a76ae84 in blink::InspectorDebuggerAgent::didPause (this=0xd98ce689410, scriptState=0xd98ce670170, callFrames=..., exception=..., hitBreakpoints=...) at ../../sky/engine/core/inspector/InspectorDebuggerAgent.cpp:1354
#11 0x00007f8a3a76b0b7 in non-virtual thunk to blink::InspectorDebuggerAgent::didPause(blink::ScriptState*, blink::ScriptValue const&, blink::ScriptValue const&, WTF::Vector<WTF::String, 0ul, WTF::DefaultAllocator> const&) ()
    at ../../sky/engine/core/inspector/InspectorDebuggerAgent.cpp:1368
#12 0x00007f8a399dae78 in blink::ScriptDebugServer::handleProgramBreak (this=0x7f8a441c5070, pausedScriptState=0xd98ce670170, executionState=..., exception=..., hitBreakpointNumbers=...) at ../../sky/engine/bindings/core/v8/ScriptDebugServer.cpp:449
#13 0x00007f8a399dbaa8 in blink::ScriptDebugServer::handleV8DebugEvent (this=0x7f8a441c5070, eventDetails=...) at ../../sky/engine/bindings/core/v8/ScriptDebugServer.cpp:519
#14 0x00007f8a399db064 in blink::ScriptDebugServer::v8DebugEventCallback (eventDetails=...) at ../../sky/engine/bindings/core/v8/ScriptDebugServer.cpp:470
#15 0x00007f8a3937bc93 in v8::internal::Debug::CallEventCallback (this=0x7f8a44015510, event=v8::Break, exec_state=..., event_data=..., client_data=0x0) at ../../v8/src/debug.cc:2826
#16 0x00007f8a3937a5af in v8::internal::Debug::ProcessDebugEvent (this=0x7f8a44015510, event=v8::Break, event_data=..., auto_continue=false) at ../../v8/src/debug.cc:2793
#17 0x00007f8a39375589 in v8::internal::Debug::OnDebugBreak (this=0x7f8a44015510, break_points_hit=..., auto_continue=false) at ../../v8/src/debug.cc:2657
#18 0x00007f8a39374132 in v8::internal::Debug::Break (this=0x7f8a44015510, args=..., frame=0x7f8a5560e958) at ../../v8/src/debug.cc:939
#19 0x00007f8a393756d0 in v8::internal::__RT_impl_Debug_Break (args=..., isolate=0x7f8a44007380) at ../../v8/src/debug.cc:982
#20 0x00007f8a3937562e in v8::internal::Debug_Break (args_length=0, args_object=0x7f8a5560eb80, isolate=0x7f8a44007380) at ../../v8/src/debug.cc:979

BUG=None
R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/743673002