Implement SmartText selection.

content/browser/android/context_selection_client.h

+// Copyright 2017 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_CONTEXT_SELECTION_CLIENT_H_
+#define CONTENT_BROWSER_ANDROID_CONTEXT_SELECTION_CLIENT_H_
+
+#include <jni.h>
+
+#include "base/android/jni_weak_ref.h"
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "base/strings/string16.h"
+
+namespace content {
+
+class WebContents;
+
+// The native portion of Java ContextSelectionClient.
+// This class performs one operation: retrieves the selected text together with
+// its surrounding context from WebContents. This surrounding text is obtained
+// asynchronously from the current focused frame and passed back to Java layer.
+class ContextSelectionClient {
+ public:
+  ContextSelectionClient(JNIEnv* env,
+                         const base::android::JavaRef<jobject>& obj,
+                         WebContents* web_contents);
+  ~ContextSelectionClient();
+
+  // Sends asynchronius request to retrieve the text.
+  void RequestSurroundingText(JNIEnv* env,
+                              const base::android::JavaParamRef<jobject>& obj,
+                              int num_extra_characters,
+                              int callback_data);
+
+  // Cancels all pending requests.
+  void CancelAllRequests(JNIEnv* env,
+                         const base::android::JavaParamRef<jobject>& obj);
+
+ private:
+  void OnSurroundingTextReceived(int callback_data,
+                                 const base::string16& text,
+                                 int start,
+                                 int end);
+
+  // A weak reference to the Java ContentSelectionClient object.
+  JavaObjectWeakGlobalRef java_ref_;
+
+  // WebContents is used to find the relevant RenderFrameHost that can send
+  // the request for the text.
+  WebContents* web_contents_;
+
+  base::WeakPtrFactory<ContextSelectionClient> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(ContextSelectionClient);
+};
+
+bool RegisterContextSelectionClient(JNIEnv* env);
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_ANDROID_CONTEXT_SELECTION_CLIENT_H_