Mark more tests flaky

third_party/WebKit/LayoutTests/TestExpectations

Index: third_party/WebKit/LayoutTests/TestExpectations
diff --git a/third_party/WebKit/LayoutTests/TestExpectations b/third_party/WebKit/LayoutTests/TestExpectations
index c11ea5d3b3a795607a4c1400930d7f9cc5e2a36c..2254a7a26a7c0e53dff12d97b055aeb720dcf3f8 100644
--- a/third_party/WebKit/LayoutTests/TestExpectations
+++ b/third_party/WebKit/LayoutTests/TestExpectations
@@ -1689,8 +1689,11 @@ crbug.com/666993 imported/wpt/html/webappapis/idle-callbacks/basic.html [ Timeou
 crbug.com/667376 imported/wpt/service-workers/cache-storage/window/cache-match.https.html [ Pass Failure ]
 crbug.com/667376 imported/wpt/service-workers/cache-storage/window/cache-put.https.html [ Pass Failure ]
 
-# Flaky on Win 7 dbg
-crbug.com/667875 [ Win7 Debug ] virtual/threaded/inspector/tracing/idle-callback.html [ Pass Failure ]
+# Flaky on Win 7 and Linux dbg
+crbug.com/667875 [ Win7 Linux Debug ] virtual/threaded/inspector/tracing/idle-callback.html [ Pass Failure ]
+
+# Flaky on Linux dbg
+crbug.com/667953 [ Linux Debug ] virtual/android/media/mediadocument/media-document-with-download-button.html [ Pass Failure ]
 
 crbug.com/664782 images/huge-image-viewport-scale.html [ NeedsRebaseline ]
 crbug.com/664782 virtual/gpu-rasterization/images/huge-image-viewport-scale.html [ NeedsRebaseline ]