Disable chromevox_tests PanelTest on msan

TBR=dmazzoni@chromium.org

Change-Id: I65cf219b1e2e89fc6889f65daedbc81e2a616e14
Reviewed-on: https://chromium-review.googlesource.com/1235017Reviewed-by: David Tseng <dtseng@chromium.org>
Commit-Queue: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592662}

chrome/browser/resources/chromeos/chromevox/cvox2/background/panel_test.extjs

@@ -26,7 +26,7 @@ PanelTest.prototype = {
     -// Flaky on dbg, see https://crbug.com/795840
     GEN_BLOCK(function() { /*!
 
-#if !defined(NDEBUG)
+#if !defined(NDEBUG) || defined(MEMORY_SANITIZER)
 #define MAYBE_ActivateMenu DISABLED_ActivateMenu
 #define MAYBE_LinkMenu DISABLED_LinkMenu
 #else