Disable ContentTextSelectionTest#testSelectActionBarPlainTextSelectAll as it is flaky.

TBR=amaralp@chromium.org
BUG=946157

Change-Id: Id4b9433a9186055073b9f3f93b95e30238172ab4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1538873Reviewed-by: Ted Choc <tedchoc@chromium.org>
Commit-Queue: Ted Choc <tedchoc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#644550}

content/public/android/javatests/src/org/chromium/content/browser/ContentTextSelectionTest.java

@@ -606,6 +606,7 @@ public class ContentTextSelectionTest {
     @Test
     @SmallTest
     @Feature({"TextSelection"})
+    @DisabledTest(message = "https://crbug.com/946157")
     public void testSelectActionBarPlainTextSelectAll() throws Exception {
         DOMUtils.longPressNode(mWebContents, "plain_text_1");
         waitForSelectActionBarVisible(true);