android: Clean up after recent refactors

Remove unused method signatures
Fix a comment

Change-Id: Idf191b76b3e2c2495a7ff3e31d16629c086d87e2
Reviewed-on: https://chromium-review.googlesource.com/847971Reviewed-by: Jinsuk Kim <jinsukkim@chromium.org>
Commit-Queue: Bo <boliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#526564}

content/browser/android/javascript_injector.h

@@ -40,7 +40,7 @@ class JavascriptInjector : public WebContentsUserData<JavascriptInjector> {
                        const base::android::JavaParamRef<jstring>& name);
 
  private:
-  // A weak reference to the Java GestureListenerManager object.
+  // A weak reference to the Java JavascriptInjectorImpl object.
   JavaObjectWeakGlobalRef java_ref_;
 
   // Manages injecting Java objects.

content/browser/web_contents/web_contents_android.h

@@ -221,28 +221,6 @@ class CONTENT_EXPORT WebContentsAndroid
       JNIEnv* env,
       const base::android::JavaParamRef<jobject>& obj);
 
-  void CreateJavaBridgeDispatcherHost(
-      JNIEnv* env,
-      const base::android::JavaParamRef<jobject>& obj,
-      const base::android::JavaParamRef<jobject>& retained_javascript_objects);
-
-  void SetAllowJavascriptInterfacesInspection(
-      JNIEnv* env,
-      const base::android::JavaParamRef<jobject>& obj,
-      jboolean allow);
-
-  void AddJavascriptInterface(
-      JNIEnv* env,
-      const base::android::JavaParamRef<jobject>& /* obj */,
-      const base::android::JavaParamRef<jobject>& object,
-      const base::android::JavaParamRef<jstring>& name,
-      const base::android::JavaParamRef<jclass>& safe_annotation_clazz);
-
-  void RemoveJavascriptInterface(
-      JNIEnv* env,
-      const base::android::JavaParamRef<jobject>& /* obj */,
-      const base::android::JavaParamRef<jstring>& name);
-
   void SetMediaSession(
       const base::android::ScopedJavaLocalRef<jobject>& j_media_session);