Make VR screen tap tests more stable

chrome/android/javatests/src/org/chromium/chrome/browser/vr_shell/WebVrTest.java

Index: chrome/android/javatests/src/org/chromium/chrome/browser/vr_shell/WebVrTest.java
diff --git a/chrome/android/javatests/src/org/chromium/chrome/browser/vr_shell/WebVrTest.java b/chrome/android/javatests/src/org/chromium/chrome/browser/vr_shell/WebVrTest.java
index 017d116dd6003235b5b1b7c751dec1f7761e8bce..ad7d9be8cdabfeb6c31472f54b9aecc03206ca6a 100644
--- a/chrome/android/javatests/src/org/chromium/chrome/browser/vr_shell/WebVrTest.java
+++ b/chrome/android/javatests/src/org/chromium/chrome/browser/vr_shell/WebVrTest.java
@@ -8,6 +8,7 @@ import static org.chromium.chrome.test.util.ChromeRestriction.RESTRICTION_TYPE_V
 import static org.chromium.chrome.test.util.ChromeRestriction.RESTRICTION_TYPE_VIEWER_NON_DAYDREAM;
 import static org.chromium.chrome.test.util.ChromeRestriction.RESTRICTION_TYPE_WEBVR_SUPPORTED;
 
+import android.os.SystemClock;
 import android.support.test.filters.SmallTest;
 
 import org.chromium.base.Log;
@@ -257,7 +258,14 @@ public class WebVrTest extends ChromeTabbedActivityTestBase {
         assertTrue("VRDisplay found", vrDisplayFound(mWebContents));
         executeStepAndWait("stepVerifyNoInitialTaps()", mWebContents);
         enterVrTapAndWait(mWebContents);
-        enterVrTap();
+        // Checking for a tap in Javascript immediately after sending one can result
+        // in the check happening before the click event is fired, which would cause
+        // this test to pass even if the click would have been registered. Solution
+        // is to send several over a short period to make sure there's enough time
+        for (int i = 0; i < 5; i++) {

[Ted C, 2017/03/27 15:44:06]

What is the goal of the test?  Are we trying to send multiple click events and
see that nothing happens?  In particular, would we want to have this in a loop,
but we don't have a reliable way to delay the next event until the previous one
was sent to the renderer?

If we did have such a mechanism, would we want to send only two events and
ensure the second event wasn't registered? 

I don't have a good suggestion for receiving acks that a event has been
processed (aside from what we suggested and that didn't work for you). 
dtrainor@ suggested there was some thing in content/ that did receive ACKs so we
could look at piping that out.  I'm fine if we want to file a new crbug and add
a TODO here though to make forward progress.

[bsheedy, 2017/03/27 20:19:12]

The purpose is to test that tapping on the screen when we're presenting in WebVR
doesn't fire any click events if the VR viewer is set to Daydream View. Ideally,
we send the first event (before we're presenting in WebVR) to enter VR (we need
a user gesture in order to do so). Then, we send a second event, somehow wait
until we know for sure that the event would have been fired in Javascript by
now, and make sure that it hasn't actually been fired.

I've talked to a couple SWEs working on the VR stuff for Chrome, and it looks
like the touch event is actually being consumed by Daydream's
DaydreamTouchListener when the viewer is set to Daydream View. I'm not exactly
familiar with what exactly that ends up affecting, but I think it doesn't even
make it to content/ in that case. If there's some way to be notified whenever
events get consumed, that could work.

+            enterVrTap();
+            SystemClock.sleep(50);
+        }
         executeStepAndWait("stepVerifyNoAdditionalTaps()", mWebContents);
         endTest(mWebContents);
     }
@@ -273,9 +281,10 @@ public class WebVrTest extends ChromeTabbedActivityTestBase {
         loadUrl(getHtmlTestFile(testName), 10);
         assertTrue("VRDisplay found", vrDisplayFound(mWebContents));
         executeStepAndWait("stepVerifyNoInitialTaps()", mWebContents);
+        // Tap and wait to enter VR
+        enterVrTapAndWait(mWebContents);
+        // Tap and wait for Javascript to receive it
         enterVrTapAndWait(mWebContents);
-        enterVrTap();
-        executeStepAndWait("stepVerifyAdditionalTap()", mWebContents);
         endTest(mWebContents);
     }