     self.explicitTests = explicitTests
     self.additionalBuildTargets = additionalBuildTargets
 
+    var envVars: [String: String]
+    if let launchActionEnvVars = launchActionEnvVars {
+      envVars = launchActionEnvVars
+    } else {
+      envVars = [:]
+    }
+
+    // Disable OS_ACTIVITY_MODE by default to cut down on Xcode 8 logging.
+    // b/31544656
+    if envVars["OS_ACTIVITY_MODE"] == nil {
+      envVars["OS_ACTIVITY_MODE"] = "disable"
+    }
+    self.launchActionEnvVars = envVars
+
     primaryTargetBuildableReference = BuildableReference(target: target,
                                                          projectBundleName: projectBundleName)
   }

  let additionalBuildTargets: [(PBXTarget, String)]?

  let primaryTargetBuildableReference: BuildableReference

  init(target: PBXTarget,
       project: PBXProject,

    }

    element.setAttributesWithDictionary(attributes)
    element.addChild(envVars(self.launchActionEnvVars))
    if launchStyle != .AppExtension {
      element.addChild(buildableProductRunnable(runnableDebuggingMode))
    } else {
