Revert of Disabled WebRtcBrowserTest.CanSetupCallAndSendDtmf (patchset #1 id:1...

Revert of Disabled WebRtcBrowserTest.CanSetupCallAndSendDtmf (patchset #1 id:1 of https://codereview.chromium.org/1133063002/)

Reason for revert:
The test should now work with the more aggressive v8 gc() after a gc fix in the test (https://codereview.chromium.org/1138073003/)

Original issue's description:
> Disabled WebRtcBrowserTest.CanSetupCallAndSendDtmf
>
> TBR=tommi
> BUG=486654
>
> Committed: https://crrev.com/fc57f2cec564c344e3e17023b41c008f574b65a7
> Cr-Commit-Position: refs/heads/master@{#329147}

TBR=henrika@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=486654

Review URL: https://codereview.chromium.org/1141533002

Cr-Commit-Position: refs/heads/master@{#329376}

content/browser/media/webrtc_browsertest.cc

@@ -164,9 +164,8 @@ IN_PROC_BROWSER_TEST_F(MAYBE_WebRtcBrowserTest,
   MakeTypicalPeerConnectionCall("call({video: true, audio: true});");
 }
 
-// TODO(henrika): see crbug.com/486654 for details why this test fails.
 IN_PROC_BROWSER_TEST_F(MAYBE_WebRtcBrowserTest,
-                       DISABLED_CanSetupCallAndSendDtmf) {
+                       MANUAL_CanSetupCallAndSendDtmf) {
   MakeTypicalPeerConnectionCall("callAndSendDtmf(\'123,abc\');");
 }