Also update ContentBrowserTest::AvailabilityNotUndefined.

BTW, I had a look at this when fixing the undefined return for getAvailability() and it seems that [SameObject] can't be used in our WebIDL implementations if it's not a readonly attribute according to the documentation. We might need to implement the mechanism in PresentationRequest.cpp directly.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9c627c11ac9fbcd803153a5bd77839cabaf29c96

commit 9c627c11ac9fbcd803153a5bd77839cabaf29c96
Author: zhaobin <zhaobin@chromium.org>
Date: Sat Dec 17 01:04:51 2016

[Presentation API] PresentationRequest::getAvailability() should return the same promise

Add a ScriptPromiseProperty to PresentationRequest to store PresentationAvailability promise object. getAvailability() will always return the same promise object.

BUG= 653131 

Review-Url: https://codereview.chromium.org/2572473003
Cr-Commit-Position: refs/heads/master@{#439269}

[modify] https://crrev.com/9c627c11ac9fbcd803153a5bd77839cabaf29c96/third_party/WebKit/LayoutTests/presentation/presentationrequest.html
[modify] https://crrev.com/9c627c11ac9fbcd803153a5bd77839cabaf29c96/third_party/WebKit/Source/modules/presentation/BUILD.gn
[modify] https://crrev.com/9c627c11ac9fbcd803153a5bd77839cabaf29c96/third_party/WebKit/Source/modules/presentation/PresentationAvailability.cpp
[modify] https://crrev.com/9c627c11ac9fbcd803153a5bd77839cabaf29c96/third_party/WebKit/Source/modules/presentation/PresentationAvailability.h
[modify] https://crrev.com/9c627c11ac9fbcd803153a5bd77839cabaf29c96/third_party/WebKit/Source/modules/presentation/PresentationAvailabilityCallbacks.cpp
[modify] https://crrev.com/9c627c11ac9fbcd803153a5bd77839cabaf29c96/third_party/WebKit/Source/modules/presentation/PresentationAvailabilityCallbacks.h
[modify] https://crrev.com/9c627c11ac9fbcd803153a5bd77839cabaf29c96/third_party/WebKit/Source/modules/presentation/PresentationAvailabilityTest.cpp
[modify] https://crrev.com/9c627c11ac9fbcd803153a5bd77839cabaf29c96/third_party/WebKit/Source/modules/presentation/PresentationConnectionCallbacks.cpp
[modify] https://crrev.com/9c627c11ac9fbcd803153a5bd77839cabaf29c96/third_party/WebKit/Source/modules/presentation/PresentationError.cpp
[modify] https://crrev.com/9c627c11ac9fbcd803153a5bd77839cabaf29c96/third_party/WebKit/Source/modules/presentation/PresentationError.h
[add] https://crrev.com/9c627c11ac9fbcd803153a5bd77839cabaf29c96/third_party/WebKit/Source/modules/presentation/PresentationPromiseProperty.h
[modify] https://crrev.com/9c627c11ac9fbcd803153a5bd77839cabaf29c96/third_party/WebKit/Source/modules/presentation/PresentationRequest.cpp
[modify] https://crrev.com/9c627c11ac9fbcd803153a5bd77839cabaf29c96/third_party/WebKit/Source/modules/presentation/PresentationRequest.h