[Android] Java Bridge: handle requests from Java Script on the background thread

content/browser/android/java/gin_java_method_invocation_helper.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_ANDROID_JAVA_GIN_JAVA_METHOD_INVOCATION_HELPER_H_
 #define CONTENT_BROWSER_ANDROID_JAVA_GIN_JAVA_METHOD_INVOCATION_HELPER_H_
 
 #include <map>
 
 #include "base/android/jni_weak_ref.h"
 #include "base/android/scoped_java_ref.h"
 #include "base/memory/ref_counted.h"
 #include "base/values.h"
 #include "content/browser/android/java/gin_java_bound_object.h"
 #include "content/browser/android/java/java_type.h"
 #include "content/common/android/gin_java_bridge_errors.h"
 #include "content/common/content_export.h"
 
 namespace content {
 
 class JavaMethod;
 
-// Instances of this class are created and initialized on the UI thread, do
-// their work on the background thread, and then again examined on the UI
-// thread. They don't work on both threads simultaneously, though.
+// Instances of this class are created and used on the background thread.
 class CONTENT_EXPORT GinJavaMethodInvocationHelper
     : public base::RefCountedThreadSafe<GinJavaMethodInvocationHelper> {
  public:
-  // DispatcherDelegate is used on the UI thread
   class DispatcherDelegate {
    public:
     DispatcherDelegate() {}
     virtual ~DispatcherDelegate() {}
     virtual JavaObjectWeakGlobalRef GetObjectWeakRef(
         GinJavaBoundObject::ObjectID object_id) = 0;
 
    private:
     DISALLOW_COPY_AND_ASSIGN(DispatcherDelegate);
   };
 
-  // ObjectDelegate is used in the background thread
   class ObjectDelegate {
    public:
     ObjectDelegate() {}
     virtual ~ObjectDelegate() {}
     virtual base::android::ScopedJavaLocalRef<jobject> GetLocalRef(
         JNIEnv* env) = 0;
     virtual base::android::ScopedJavaLocalRef<jclass> GetLocalClassRef(
         JNIEnv* env) = 0;
     virtual const JavaMethod* FindMethod(const std::string& method_name,
                                          size_t num_parameters) = 0;
     virtual bool IsObjectGetClassMethod(const JavaMethod* method) = 0;
     virtual const base::android::JavaRef<jclass>& GetSafeAnnotationClass() = 0;
 
    private:
     DISALLOW_COPY_AND_ASSIGN(ObjectDelegate);
   };
 
   GinJavaMethodInvocationHelper(scoped_ptr<ObjectDelegate> object,
                                 const std::string& method_name,
                                 const base::ListValue& arguments);
   void Init(DispatcherDelegate* dispatcher);
 
-  // Called on the background thread
   void Invoke();
 
-  // Called on the UI thread
   bool HoldsPrimitiveResult();
   const base::ListValue& GetPrimitiveResult();
   const base::android::JavaRef<jobject>& GetObjectResult();
   const base::android::JavaRef<jclass>& GetSafeAnnotationClass();
   const GinJavaBridgeError GetInvocationError();
 
  private:
   friend class base::RefCountedThreadSafe<GinJavaMethodInvocationHelper>;
   ~GinJavaMethodInvocationHelper();
 
-  // Called on the UI thread
   void BuildObjectRefsFromListValue(DispatcherDelegate* dispatcher,
                                     const base::Value* list_value);
   void BuildObjectRefsFromDictionaryValue(DispatcherDelegate* dispatcher,
                                           const base::Value* dict_value);
 
   bool AppendObjectRef(DispatcherDelegate* dispatcher,
                        const base::Value* raw_value);
 
-  // Called on the background thread.
   void InvokeMethod(jobject object,
                     jclass clazz,
                     const JavaType& return_type,
                     jmethodID id,
                     jvalue* parameters);
   void SetInvocationError(GinJavaBridgeError error);
   void SetPrimitiveResult(const base::ListValue& result_wrapper);
   void SetObjectResult(
       const base::android::JavaRef<jobject>& object,
       const base::android::JavaRef<jclass>& safe_annotation_clazz);
@@ skipping 10 matching lines @@
   GinJavaBridgeError invocation_error_;
   base::android::ScopedJavaGlobalRef<jobject> object_result_;
   base::android::ScopedJavaGlobalRef<jclass> safe_annotation_clazz_;
 
   DISALLOW_COPY_AND_ASSIGN(GinJavaMethodInvocationHelper);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_ANDROID_JAVA_GIN_JAVA_METHOD_INVOCATION_HELPER_H_