Completed the code path from AndroidProviderService to HistoryBackend.

chrome/browser/android_provider_service.h

Index: chrome/browser/android_provider_service.h
diff --git a/chrome/browser/android_provider_service.h b/chrome/browser/android_provider_service.h
new file mode 100644
index 0000000000000000000000000000000000000000..c8209407c5a809ec1e4a38decaf7e53ba57f1bb5
--- /dev/null
+++ b/chrome/browser/android_provider_service.h
@@ -0,0 +1,147 @@
+// Copyright (c) 2012 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 CHROME_BROWSER_ANDROID_PROVIDER_SERVICE_H_

[sky, 2012/04/25 15:57:25]

This class is named too generically, additionally chrome/browser is too high
level for this. How about moving it to chrome/browser/history/android and naming
it android_history_provider_service?

[michaelbai, 2012/04/26 05:32:48]

Done.

+#define CHROME_BROWSER_ANDROID_PROVIDER_SERVICE_H_
+
+#include "base/callback.h"
+#include "base/memory/ref_counted.h"
+#include "chrome/browser/cancelable_request.h"
+#include "chrome/browser/history/android/android_history_types.h"
+#include "sql/statement.h"
+
+class Profile;
+
+// This class provides the methods to communicate with history backend service
+// for Android content provider.

[sky, 2012/04/25 15:57:25]

the Android cont...

[michaelbai, 2012/04/26 05:32:48]

Done.

+// The methods of this class should run in UI thread to cooperate with the

[sky, 2012/04/25 15:57:25]

should -> must
on the UI thread

[michaelbai, 2012/04/26 05:32:48]

Done.

+// BookmarkModel task posted in DB thread.
+// To be a subclass of RefCountedThreadSafe is convenient for the caller which

[sky, 2012/04/25 15:57:25]

I don't get this comment. Your earlier comment says this is used on the UI
thread, but then mention the Java thread. Are they separate? Are they the same?
Either way, just because two threads are using the same objects doesn't
necessitate the object being ref counted thread safe. What needs to be clear is
who owns the object. If there is no clear owner (typically bad), then ref
counted makes sense.
Is there one clear owner of this object?

[michaelbai, 2012/04/26 05:32:48]

You are right! I removed RefCounted, it is not necessary.

On 2012/04/25 15:57:25, sky wrote:

+// always runs in the Java thread.
+class AndroidProviderService : public CancelableRequestProvider,
+          public base::RefCountedThreadSafe<AndroidProviderService> {
+ public:
+  explicit AndroidProviderService(Profile* profile);
+
+  // The callback definitions ------------------------------------------------
+  typedef base::Callback<void(
+                    Handle,                // handle
+                    bool,                  // true if the query succeeded.
+                    history::AndroidStatement*)>  // the result of query
+                    QueryCallback;
+  typedef CancelableRequest<QueryCallback> QueryRequest;
+
+  typedef base::Callback<void(
+                    Handle,                // handle
+                    bool,                  // true if the update succeeded.
+                    int)>                  // the number of row updated.
+                    UpdateCallback;
+  typedef CancelableRequest<UpdateCallback> UpdateRequest;
+
+  typedef base::Callback<void(
+                    Handle,                // handle
+                    bool,                  // true if the insert succeeded.
+                    int64)>                // the id of inserted row.
+                    InsertCallback;
+  typedef CancelableRequest<InsertCallback> InsertRequest;
+
+  typedef base::Callback<void(
+                    Handle,                // handle
+                    bool,                  // true if the deletion succeeded.
+                    int)>                  // the number of row deleted.
+                    DeleteCallback;
+  typedef CancelableRequest<DeleteCallback> DeleteRequest;
+
+  typedef base::Callback<void(
+                    Handle,                // handle
+                    int)>                  // the new position.
+                    MoveStatementCallback;
+  typedef CancelableRequest<MoveStatementCallback> MoveStatementRequest;
+
+  // History and Bookmarks ----------------------------------------------------
+
+  void QueryHistoryAndBookmarks(

[sky, 2012/04/25 15:57:25]

Add descriptions for all of the methods.

[michaelbai, 2012/04/26 05:32:48]

Done.

+      const std::vector<history::HistoryAndBookmarkRow::ColumnID>& projections,
+      const std::string selection,
+      const std::vector<string16>& selection_args,
+      const std::string sort_order,
+      CancelableRequestConsumerBase* consumer,
+      const QueryCallback& callback);
+
+  void UpdateHistoryAndBookmarks(const history::HistoryAndBookmarkRow& row,
+                                 const std::string& selection,
+                                 const std::vector<string16>& selection_args,
+                                 CancelableRequestConsumerBase* consumer,
+                                 const UpdateCallback& callback);
+
+  void DeleteHistoryAndBookmarks(const std::string& selection,
+                                 const std::vector<string16>& selection_args,
+                                 CancelableRequestConsumerBase* consumer,
+                                 const DeleteCallback& callback);
+
+  void InsertHistoryAndBookmark(const history::HistoryAndBookmarkRow& values,
+                                CancelableRequestConsumerBase* consumer,
+                                const InsertCallback& callback);
+
+  void DeleteHistory(const std::string& selection,
+                     const std::vector<string16>& selection_args,
+                     CancelableRequestConsumerBase* consumer,
+                     const DeleteCallback& callback);
+
+  // Statement ----------------------------------------------------------------
+  // Moved the statement's current row from |current_pos| to |destination| in DB
+  // thread. The new position will be returned in the callback and might not be
+  // the |destination| if the |destination| isn't less than the count of rows.
+  void MoveStatement(history::AndroidStatement* statement,
+                     int current_pos,
+                     int destination,
+                     CancelableRequestConsumerBase* consumer,
+                     const MoveStatementCallback& callback);
+
+  // Asks to close the statement in database thread. The ownership of
+  // |statement| is transferred.
+  void CloseStatement(history::AndroidStatement* statement);
+
+  // Search term --------------------------------------------------------------
+  void InsertSearchTerm(const history::SearchRow& row,
+                        CancelableRequestConsumerBase* consumer,
+                        const InsertCallback& callback);
+
+  void UpdateSearchTerms(const history::SearchRow& row,
+                         const std::string& selection,
+                         const std::vector<string16>& selection_args,
+                         CancelableRequestConsumerBase* consumer,
+                         const UpdateCallback& callback);
+
+  void DeleteSearchTerms(const std::string& selection,
+                         const std::vector<string16>& selection_args,
+                         CancelableRequestConsumerBase* consumer,
+                         const DeleteCallback& callback);
+
+  void QuerySearchTerms(
+      const std::vector<history::SearchRow::ColumnID>& projections,
+      const std::string selection,
+      const std::vector<string16>& selection_args,
+      const std::string sort_order,
+      CancelableRequestConsumerBase* consumer,
+      const QueryCallback& callback);
+
+ private:
+  friend class base::RefCountedThreadSafe<AndroidProviderService>;
+
+  virtual ~AndroidProviderService();
+
+  void ForwardEmptyInsertResultAsync(InsertRequest* request);
+  void ForwardEmptyQueryResultAsync(QueryRequest* request);
+  void ForwardEmptyUpdateResultAsync(UpdateRequest* request);
+  void ForwardEmptyDeleteResultAsync(UpdateRequest* request);
+  void ForwardEmptyMoveStatementResultAsync(MoveStatementRequest* request,
+                                            int value);
+
+  Profile* profile_;
+
+  DISALLOW_COPY_AND_ASSIGN(AndroidProviderService);
+};
+
+#endif  // CHROME_BROWSER_ANDROID_PROVIDER_SERVICE_H_