Update mediasource-duration-expected to PASS and mark flaky temporarily

Chromium-side patch that removes suppressing asynch processing of
redundant MSE seeks (https://codereview.chromium.org/1305273007/)
appears to have changed behavior enough on at least desktop Chromium
that the mediasource-duration layout test now shows "PASS" for each test
within it. This change updates those expectations to PASS (by removing
the expectations file) and marks the test flaky in preparation
for landing the Chromium-side change.

TBR=philipj@opera.com
BUG=526337, 399523, 303419, 284782, 266631
TEST=http/tests/media/media-source/mediasource-duration.html

Review URL: https://codereview.chromium.org/1321253005

git-svn-id: svn://svn.chromium.org/blink/trunk@201511 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/LayoutTests/TestExpectations

@@ -729,6 +729,8 @@ crbug.com/302729 [ Android ] http/tests/media/media-source/mediasource-seek-beyo
 crbug.com/524160 [ Debug ] http/tests/media/media-source/mediasource-appendbuffer-quota-exceeded.html [ Timeout ]
 crbug.com/524160 [ Debug ] http/tests/media/media-source/mediasource-appendstream-quota-exceeded.html [ Timeout ]
 
+crbug.com/526337 http/tests/media/media-source/mediasource-duration.html [ Pass Failure ]
+
 crbug.com/517449 [ Android ] css3/images/optimize-contrast-image.html [ ImageOnlyFailure ]
 
 crbug.com/309675 compositing/gestures/gesture-tapHighlight-simple-longPress.html [ ImageOnlyFailure ]

third_party/WebKit/LayoutTests/http/tests/media/media-source/mediasource-duration-expected.txt

-This is a testharness.js-based test.
-FAIL Test seek starts on duration truncation below currentTime assert_true: mediaElement.seeking while seeking to truncatedDuration expected true got false
-FAIL Test appendBuffer completes previous seek to truncated duration assert_true: mediaElement.seeking while seeking to truncatedDuration expected true got false
-FAIL Test endOfStream completes previous seek to truncated duration assert_true: mediaElement.seeking while seeking to truncatedDuration expected true got false
-PASS Test setting same duration multiple times does not fire duplicate durationchange 
-Harness: the test ran to completion.
-