Flakyness: mark equivalent-background-image-no-transition.html flaky on Win10.

Full path: transitions/equivalent-background-image-no-transition.html

It seems to be failing consistanly every other day.

BUG=521764
NOTRY=true
TBR=schenney@chromium.org

Review URL: https://codereview.chromium.org/1311413005

git-svn-id: svn://svn.chromium.org/blink/trunk@201558 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/LayoutTests/TestExpectations

@@ -1528,6 +1528,7 @@ crbug.com/521764 [ Win10 ] svg/custom/textPath-remove-path-pattern.svg [ ImageOn
 crbug.com/521764 [ Win10 ] accessibility/inline-text-changes.html [ Failure Pass ]
 crbug.com/521764 [ Win10 ] fast/loader/javascript-detached-frame-no-crash.html [ Pass Timeout ]
 crbug.com/521764 [ Win10 ] virtual/display_list_2d_canvas/fast/canvas/canvas-resize-reset.html [ Pass Timeout ]
+crbug.com/521764 [ Win10 ] transitions/equivalent-background-image-no-transition.html [ Pass Timeout ]
 
 # GrGLConvolutionEffect optimization causes blink layout test image differences
 crbug.com/505086 css3/filters/effect-blur-hw.html [ NeedsManualRebaseline ]