Add Accessibility Object Model to content features, and add a browser test.

content/child/runtime_features.cc

Index: content/child/runtime_features.cc
diff --git a/content/child/runtime_features.cc b/content/child/runtime_features.cc
index 4eec4971c3f3377e94178c83371ca57bbdf6973f..b783df3bdd63ad83df54c5ef83fcb5d74ad293b0 100644
--- a/content/child/runtime_features.cc
+++ b/content/child/runtime_features.cc
@@ -317,6 +317,9 @@ void SetRuntimeFeaturesDefaultsAndUpdateFromArgs(
           features::kSendBeaconThrowForBlobWithNonSimpleType))
     WebRuntimeFeatures::enableSendBeaconThrowForBlobWithNonSimpleType(true);
 
+  WebRuntimeFeatures::enableAccessibilityObjectModel(
+      base::FeatureList::IsEnabled(features::kAccessibilityObjectModel));

[esprehn, 2017/04/04 19:06:20]

Why features:: instead of switches:: This is different from all the other things
here like switches::kRootLayerScrolls

[dmazzoni, 2017/04/04 19:28:16]

I think features are more flexible, right? We get things
like field trials / experiments, and we don't need another
top-level command-line switch if we don't want one (you
can enable the feature with --enable-features=).

[esprehn, 2017/04/04 19:59:44]

Ah okay that makes sense, is there a doc somewhere that explains this? I wonder
if some of the existing switches should be converted.

+
 #if defined(OS_ANDROID)
   if (command_line.HasSwitch(switches::kDisableMediaSessionAPI))
     WebRuntimeFeatures::enableMediaSession(false);