Fuchsia: add filter entries for long-running net tests on ARM.

These tests take a very long time to execute on emulated ARM cores,
but they do pass on real ARM hardware.

Bug: 780652
Change-Id: Iaa608ab980dd63616b9c44b4e5b386340af2664b
Reviewed-on: https://chromium-review.googlesource.com/750076
Commit-Queue: Kevin Marshall <kmarshall@chromium.org>
Reviewed-by: Scott Graham <scottmg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#515228}

testing/buildbot/filters/fuchsia.net_unittests.filter

@@ -10,3 +10,7 @@
 # base::MakeFileUnreadable() doesn't work. https://crbug.com/759853
 -HttpNetworkTransactionTest.UploadUnreadableFile
 -SpdyNetworkTransactionTest.UnreadableFilePost
+
+# These stress tests take a very long time on emulated ARM cores.
+-SupportedVersion/QuicConnectionTest.TooManySentPackets/*
+-RangeOfTreeSizes/CTLogVerifierTestUsingGenerator.VerifiesValidConsistencyProof/*