Bind Window focus ability to the ExecutionContext instead of the process.

Source/modules/serviceworkers/ServiceWorkerClient.cpp

Index: Source/modules/serviceworkers/ServiceWorkerClient.cpp
diff --git a/Source/modules/serviceworkers/ServiceWorkerClient.cpp b/Source/modules/serviceworkers/ServiceWorkerClient.cpp
index 66bf83136b0992896cd2d75158702d4e02196821..f7fb5f2841421e7593c9244dfba586491d4409e8 100644
--- a/Source/modules/serviceworkers/ServiceWorkerClient.cpp
+++ b/Source/modules/serviceworkers/ServiceWorkerClient.cpp
@@ -9,6 +9,7 @@
 #include "bindings/core/v8/ExceptionState.h"
 #include "bindings/core/v8/ScriptPromiseResolver.h"
 #include "bindings/core/v8/SerializedScriptValue.h"
+#include "core/page/WindowFocusAllowedIndicator.h"
 #include "modules/serviceworkers/ServiceWorkerError.h"
 #include "modules/serviceworkers/ServiceWorkerGlobalScopeClient.h"
 #include "public/platform/WebString.h"
@@ -73,9 +74,11 @@ ScriptPromise ServiceWorkerClient::focus(ScriptState* scriptState)
     RefPtr<ScriptPromiseResolver> resolver = ScriptPromiseResolver::create(scriptState);
     ScriptPromise promise = resolver->promise();
 
-    // FIXME: there should be a check for whether the caller is allowed to focus
-    // the client. The promise should succeed with |false| if the call is not
-    // allowed. https://crbug.com/437149
+    if (!scriptState->executionContext()->isWindowFocusAllowed()) {
+        resolver->resolve(false);
+        return promise;
+    }
+    scriptState->executionContext()->consumeWindowFocus();
 
     ServiceWorkerGlobalScopeClient::from(scriptState->executionContext())->focus(m_id, new CallbackPromiseAdapter<bool, ServiceWorkerError>(resolver));
     return promise;