Filter some delicious buttery, crumbly, flaky tests.

Add the following tests to the Fuchsia filter for content_unittests:

- BluetoothBlocklistTest.InvalidUUID
- RenderWidgetHostViewAuraTest.SyntheticFlingCancelAtTouchpadScrollBegin
- WebBluetoothDeviceIdTest.DefaultConstructor

Bug: 776424, 867502
Change-Id: I7e588b3946e640cb77b46cace1ef8ab79385f5b8
Reviewed-on: https://chromium-review.googlesource.com/1150803
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578804}

testing/buildbot/filters/fuchsia.content_unittests.filter

 # Being ported, https://crbug.com/754861.
 
+# https://crbug.com/780317 - Flakily timeout under QEMU s/w emulation of ARM64.
+-BluetoothBlocklistTest.InvalidUUID
+-WebBluetoothDeviceIdTest.DefaultConstructor
+
 # These rely on chmod() for MakeFileUnread/writable(), https://crbug.com/759853.
 -BaseFileTest.ReadonlyBaseFile
 -BaseFileTest.RenameWithError
@@ -58,4 +62,5 @@
 -RenderWidgetHostViewAuraOverscrollTest.GestureScrollDebounceOverscrolls
 -RenderWidgetHostViewAuraOverscrollTest.GestureScrollDebounceTimerOverscroll
 -RenderWidgetHostViewAuraOverscrollTest.TouchGestureEndDispatchedAfterOverscrollComplete
+-RenderWidgetHostViewAuraTest.SyntheticFlingCancelAtTouchpadScrollBegin
 -RenderWidgetHostViewAuraTest.TimerBasedWheelEventPhaseInfo