Make new WebUSB implementation more resilient to garbage collection.

third_party/WebKit/LayoutTests/TestExpectations

 # ====== Oilpan-only failures from here ======
 # Most of these actually cause the tests to report success, rather than
 # failure. Expected outputs will be adjusted for the better once Oilpan
 # has been well and truly enabled always.
 
 # With Oilpan, the parent pointer in the CSSRule hierarchy is
 # strong. This is the intended behavior.
 crbug.com/345630 fast/dom/StyleSheet/gc-parent-rule.html [ Failure ]
 crbug.com/345630 fast/dom/StyleSheet/gc-parent-stylesheet.html [ Failure ]
 crbug.com/345655 fast/dom/StyleSheet/detached-parent-rule-without-wrapper.html [ Failure ]
@@ skipping 1242 matching lines @@
 crbug.com/594672 virtual/pointerevent/fast/events/scale-and-scroll-iframe-window.html [ Failure Pass ]
 crbug.com/594672 virtual/pointerevent/fast/events/updateLayoutForHitTest.html [ Failure Pass ]
 crbug.com/594672 virtual/trustedeventsdefaultaction/fast/events/iframe-object-onload.html [ Failure Pass ]
 crbug.com/594672 virtual/trustedeventsdefaultaction/fast/events/scale-and-scroll-iframe-body.html [ Failure Pass ]
 crbug.com/594672 virtual/trustedeventsdefaultaction/fast/events/updateLayoutForHitTest.html [ Failure Pass ]
 
 crbug.com/593888 [ Linux Debug ] fast/dom/htmlcollection-reachable.html [ Timeout ]
 
 crbug.com/605515 svg/batik/filters/feTile.svg [ NeedsManualRebaseline ]
 
-crbug.com/605487 [ Win ] fast/dom/Window/property-access-on-cached-properties-after-frame-navigated.html [ Crash ]
-crbug.com/605487 [ Win ] fast/dom/Window/property-access-on-cached-properties-after-frame-removed-and-gced.html [ Crash ]
-crbug.com/605487 [ Win ] fast/dom/Window/property-access-on-cached-properties-after-frame-removed.html [ Crash ]
-crbug.com/605487 [ Win ] fast/dom/Window/property-access-on-cached-window-after-frame-navigated.html [ Crash ]
-crbug.com/605487 [ Win ] fast/dom/Window/property-access-on-cached-window-after-frame-removed-and-gced.html [ Crash ]
-crbug.com/605487 [ Win ] fast/dom/Window/property-access-on-cached-window-after-frame-removed.html [ Crash ]
-crbug.com/605487 [ Win ] usb/usb.html [ Crash ]
-crbug.com/605487 [ Win ] usb/usbDevice.html  [ Crash ]
-
 crbug.com/540528 [ Linux ] intersection-observer/remove-element.html [ Leak ]
 crbug.com/603728 [ Linux ] virtual/gpu-rasterization/fast/images/color-profile-filter.html [ Failure Timeout Pass ]
 
 crbug.com/593568 [ Win Debug ] virtual/threaded/fast/scroll-behavior/smooth-scroll/horizontal-smooth-scroll-in-rtl.html [ Failure ]
 
 #crbug.com/591825 [ Mac10.11 Debug ] fast/text/selection-multiple-runs.html [ Failure ]
 
 crbug.com/591832 [ Mac10.11 Retina ] compositing/overflow/do-not-paint-outline-into-composited-scrolling-contents.html [ Failure ]
 crbug.com/591832 [ Mac10.11 Retina ] compositing/overflow/update-widget-positions-on-nested-frames-and-scrollers.html [ Failure ]
 
@@ skipping 236 matching lines @@
 crbug.com/603703 [ Linux ] imported/web-platform-tests/web-animations/animation-timeline/document-timeline.html [ Failure Pass ]
 
 crbug.com/600248 imported/web-platform-tests/web-animations/animation-effect-timing/endDelay.html [ Failure ]
 crbug.com/600248 imported/web-platform-tests/web-animations/animation/constructor.html [ Failure Timeout ]
 
 crbug.com/604642 [ Mac ]  fast/text/midword-break-after-breakable-char.html [ Failure ]
 
 crbug.com/605047 [ Mac10.11 Retina ] fast/text/emphasis.html [ Failure ]
 
 crbug.com/605059 [ Retina ] fast/text/international/rtl-negative-letter-spacing.html [ Failure ]