Revert of Disable...

Revert of Disable WebContentsObserverAndroidTest#testDidFirstVisuallyNonEmptyPaint (patchset #1 id:1 of https://codereview.chromium.org/554713002/)

Reason for revert:
Compile error... I'll have to look into this.

Original issue's description:
> Disable WebContentsObserverAndroidTest#testDidFirstVisuallyNonEmptyPaint
>
> It broke on Android Tests (dbg)
>
> http://build.chromium.org/p/chromium.webkit/builders/Android%20Tests%20%28dbg%29/builds/21342
>
> [FAIL] org.chromium.content.browser.WebContentsObserverAndroidTest#testDidFirstVisuallyNonEmptyPaint:
> java.util.concurrent.TimeoutException: waitForCallback timed out!
>   at org.chromium.content.browser.test.util.CallbackHelper.waitForCallback(CallbackHelper.java:183)
>   at org.chromium.content.browser.test.util.CallbackHelper.waitForCallback(CallbackHelper.java:191)
>   at org.chromium.content.browser.test.util.CallbackHelper.waitForCallback(CallbackHelper.java:197)
>   at org.chromium.content.browser.WebContentsObserverAndroidTest.testDidFirstVisuallyNonEmptyPaint(WebContentsObserverAndroidTest.java:70)
>   at java.lang.reflect.Method.invokeNative(Native Method)
>   at android.test.InstrumentationTestCase.runMethod(InstrumentationTestCase.java:214)
>   at android.test.InstrumentationTestCase.runTest(InstrumentationTestCase.java:199)
>   at android.test.ActivityInstrumentationTestCase2.runTest(ActivityInstrumentationTestCase2.java:192)
>   at org.chromium.content_shell_apk.ContentShellTestBase.runTest(ContentShellTestBase.java:227)
>   at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:191)
>   at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:176)
>   at android.test.InstrumentationTestRunner.onStart(InstrumentationTestRunner.java:554)
>
> BUG=411931
> TBR=keishi, reed
>
> Committed: https://chromium.googlesource.com/chromium/src/+/833089c8f5bec9a81323cbb314689f9569eb6ec8

TBR=keishi@chromium.org,reed@android.com
NOTREECHECKS=true
NOTRY=true
BUG=411931

Review URL: https://codereview.chromium.org/551043003

Cr-Commit-Position: refs/heads/master@{#293742}

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

@@ -49,12 +49,8 @@ public class WebContentsObserverAndroidTest extends ContentShellTestBase {
         waitForActiveShellToBeDoneLoading();
     }
 
-    /*
     @SmallTest
     @Feature({"Navigation"})
-    http://crbug.com/411931
-    */
-    @DisabledTest
     public void testDidFirstVisuallyNonEmptyPaint() throws Throwable {
         TestWebContentsObserverAndroid observer = ThreadUtils.runOnUiThreadBlocking(
                 new Callable<TestWebContentsObserverAndroid>() {