Revert "Disable testFlingScroll"

This reverts commit 74872d88.

Reason for revert: Test was failing due to the device screen being locked, not a problem with this specific test.

Original change's description:
> Disable testFlingScroll
>
> Disable
> org.chromium.android_webview.test.AndroidScrollIntegrationTest#testFlingScroll
> due to flaky
>
> Bug: 1147938
> Change-Id: Ic701876e9c09399309b06827d1384b665b9b9509
> Tbr: boliu@chromium.org
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2535554
> Reviewed-by: Owen Min <zmin@chromium.org>
> Commit-Queue: Owen Min <zmin@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#826959}

TBR=boliu@chromium.org,zmin@chromium.org,dbertoni@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1147938
Change-Id: I135d770ca7a98a56a00b3b617db6b69d787b845f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2541649Reviewed-by: Owen Min <zmin@chromium.org>
Reviewed-by: Nate Fischer <ntfschr@chromium.org>
Commit-Queue: Richard Coles <torne@chromium.org>
Commit-Queue: Nate Fischer <ntfschr@chromium.org>
Auto-Submit: Richard Coles <torne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827889}

android_webview/javatests/src/org/chromium/android_webview/test/AndroidScrollIntegrationTest.java

@@ -567,7 +567,6 @@ public class AndroidScrollIntegrationTest {
     @Test
     @SmallTest
     @Feature({"AndroidWebView"})
-    @DisabledTest(message = "crbug.com/1147938")
     public void testFlingScroll() throws Throwable {
         final TestAwContentsClient contentsClient = new TestAwContentsClient();
         final ScrollTestContainerView testContainerView =