Revert of Disable WebContentsObserverAndroidTest#testDidFirstVisuallyNonEmptyPaint

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
Committed: https://crrev.com/d5708db974a00297a2430ea24bffda18624d8974
Cr-Commit-Position: refs/heads/master@{#293742}

[arv (Not doing code reviews), 2014-09-08 16:40:21]

Created Revert of Disable
WebContentsObserverAndroidTest#testDidFirstVisuallyNonEmptyPaint

[commit-bot: I haz the power, 2014-09-08 16:41:21]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/arv@chromium.org/551043003/1

[arv (Not doing code reviews), 2014-09-08 16:42:10]

The CQ bit was unchecked by arv@chromium.org

[commit-bot: I haz the power, 2014-09-08 16:44:14]

Committed patchset #1 (id:1) as 5acb0b378b1fab2bf6ceb56809e33b9d77993b34

[commit-bot: I haz the power, 2014-09-10 03:46:48]

Patchset 1 (id:??) landed as
https://crrev.com/d5708db974a00297a2430ea24bffda18624d8974
Cr-Commit-Position: refs/heads/master@{#293742}