Remove flaky TestExpectations for tests which appear non-flaky recently.

This change was made by the update-test-expectations script.

Recent test results history:
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=webkit_layout_tests&tests=http/tests/appcache/abort-cache-onchecking-resource-404.html,http/tests/d
om/create-contextual-fragment-from-svg-document-range.html,http/tests/cache/zero-length-xhr.html

Bug: 762008, 762399, 762423
Change-Id: If563520cb19cc426ddf93581570cfb3d4b76f7d5
Reviewed-on: https://chromium-review.googlesource.com/1062601Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Quinten Yearsley <qyearsley@chromium.org>
Cr-Commit-Position: refs/heads/master@{#559332}

third_party/WebKit/LayoutTests/TestExpectations

@@ -4304,9 +4304,6 @@ crbug.com/770232 [ Win10 ] editing/selection/paint-hyphen.html [ Failure ]
 crbug.com/770232 [ Win10 ] fast/text/hyphenate-character.html [ Failure ]
 crbug.com/770232 [ Win10 ] fast/text/unicode-fallback-font.html [ Failure ]
 
-# Test flaky (crashing) on WebKit Android (Nexus4)
-crbug.com/762008 [ Android ] http/tests/appcache/abort-cache-onchecking-resource-404.html [ Pass Crash ]
-
 # Editing commands incorrectly assume no plain text length change after formatting text.
 crbug.com/764489 editing/execCommand/format-block-multiple-paragraphs.html [ Failure ]
 crbug.com/764489 editing/execCommand/format-block-multiple-paragraphs-in-pre.html [ Failure ]
@@ -4314,10 +4311,6 @@ crbug.com/764489 editing/execCommand/format-block-multiple-paragraphs-in-pre.htm
 # Incorrect pixel alignment due to float number scale factor.
 crbug.com/773810 external/wpt/css/css-transforms/transform3d-perspective-008.html [ Failure ]
 
-# Sheriff failure 2017-09-06
-crbug.com/762423 [ Android ] http/tests/dom/create-contextual-fragment-from-svg-document-range.html [ Pass Crash ]
-crbug.com/762399 [ Android ] http/tests/cache/zero-length-xhr.html [ Pass Crash ]
-
 # Sheriff failures 2017-09-08
 crbug.com/763667 external/wpt/upgrade-insecure-requests/iframe-redirect-upgrade.https.html [ Timeout ]