Disable SyntheticMouseEventTest.MouseEventAck, flaking

TBR: avi@chromium.org
Bug: 790751
Change-Id: Ic8f16dda831989e3d2af60a96da3b3fc4cb39974
Reviewed-on: https://chromium-review.googlesource.com/802177Reviewed-by: Scott Graham <scottmg@chromium.org>
Commit-Queue: Scott Graham <scottmg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#520742}

content/browser/devtools/protocol/devtools_protocol_browsertest.cc

@@ -582,7 +582,7 @@ IN_PROC_BROWSER_TEST_F(SyntheticKeyEventTest, KeyboardEventAck) {
   EXPECT_EQ(3u, result_ids_.size());
 }
 
-IN_PROC_BROWSER_TEST_F(SyntheticMouseEventTest, MouseEventAck) {
+IN_PROC_BROWSER_TEST_F(SyntheticMouseEventTest, DISABLED_MouseEventAck) {
   NavigateToURLBlockUntilNavigationsComplete(shell(), GURL("about:blank"), 1);
   Attach();
   ASSERT_TRUE(content::ExecuteScript(