Reland "Disable 2 layout tests after r548309 and add a TODO to reenable them"

This reverts commit 6963de52.

Reason for revert: Wanted to land without NOTRY=true

Original change's description:
> Revert "Disable 2 layout tests after r548309 and add a TODO to reenable them"
> 
> This reverts commit f4132695.
> 
> Reason for revert: Rebaselining and reenabling the tests
> 
> Original change's description:
> > Disable 2 layout tests after r548309 and add a TODO to reenable them
> > 
> > BUG=787020
> > TBR=eae
> > 
> > Change-Id: I9931e0f0c73a6a0bb7dbade9c8c189acec1cb9d2
> > Reviewed-on: https://chromium-review.googlesource.com/997174
> > Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#548331}
> 
> TBR=eae@chromium.org,thomasanderson@chromium.org
> 
> Change-Id: Ifd643ac484dc11bbd4f922bd01445e94b7f88f53
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: 787020
> Reviewed-on: https://chromium-review.googlesource.com/997113
> Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
> Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
> Reviewed-by: Emil A Eklund <eae@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#548348}

TBR=eae@chromium.org,thomasanderson@chromium.org

Change-Id: Ibad78cf3b62ec0995708a425d0855449aaf3d04a
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 787020
Reviewed-on: https://chromium-review.googlesource.com/997182Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548350}

third_party/WebKit/LayoutTests/TestExpectations

@@ -3994,6 +3994,10 @@ crbug.com/827209 virtual/mouseevent_fractional/fast/events/middleClickAutoscroll
 # Utility for manual testing, not intended to be run as part of layout tests.
 crbug.com/785955 http/tests/credentialmanager/tools/virtual-authenticator-environment-manual.html [ Skip ]
 
+# Disabled after r548309.  TODO(thomasanderson): Reenable these tests
+crbug.com/787020 virtual/gpu/fast/canvas/canvas-zero-length-lineCap.html [ Pass Failure ]
+crbug.com/787020 virtual/threaded/http/tests/devtools/tracing/timeline-js/compile-script.js [ Pass Failure ]
+
 # These Web Authentication API would require either real hardware, or
 # virtual simulation thereof (work in progress, see: https://crbug.com/785955).
 crbug.com/826936 external/wpt/webauthn/createcredential-badargs-authnrselection.https.html [ Pass Timeout ]