Enable mojo based synchronous compositor

Turn off disabling mojo input messages for webview. That will enable
the mojo input channel and the mojo synchronous compositor input channel.

BUG=722928

Change-Id: I14ae3d3a83405eb9c6a228f7f08171dab3ca86f2
Reviewed-on: https://chromium-review.googlesource.com/898553
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Reviewed-by: Bo <boliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#539127}

android_webview/lib/aw_main_delegate.cc

@@ -157,8 +157,6 @@ bool AwMainDelegate::BasicStartupComplete(int* exit_code) {
   CommandLineHelper::AddDisabledFeature(*cl,
                                         media::kMediaDrmPersistentLicense.name);
 
-  CommandLineHelper::AddDisabledFeature(*cl, features::kMojoInputMessages.name);
-
   CommandLineHelper::AddEnabledFeature(
       *cl, autofill::features::kAutofillSkipComparingInferredLabels.name);