[Sync] Make GetFirstChildId return a flag indicating success

chrome/browser/sync/syncable/syncable.h

 // Copyright (c) 2011 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_SYNC_SYNCABLE_SYNCABLE_H_
 #define CHROME_BROWSER_SYNC_SYNCABLE_SYNCABLE_H_
 #pragma once
 
 #include <algorithm>
 #include <bitset>
 #include <cstddef>
 #include <iosfwd>
 #include <limits>
 #include <map>
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/atomicops.h"
 #include "base/basictypes.h"
+#include "base/compiler_specific.h"
 #include "base/file_path.h"
 #include "base/gtest_prod_util.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/observer_list_threadsafe.h"
 #include "base/synchronization/lock.h"
 #include "base/time.h"
 #include "chrome/browser/sync/protocol/sync.pb.h"
 #include "chrome/browser/sync/syncable/blob.h"
@@ skipping 887 matching lines @@
 
   // Returns the child meta handles (even those for deleted/unlinked
   // nodes) for given meta handle.  Clears |result| if there are no
   // children.
   void GetChildHandlesByHandle(BaseTransaction*, int64 handle,
       ChildHandles* result);
 
   // Returns true iff |id| has children.
   bool HasChildren(BaseTransaction* trans, const Id& id);
 
-  // Find the first or last child in the positional ordering under a parent,
-  // and return its id.  Returns a root Id if parent has no children.
-  Id GetFirstChildId(BaseTransaction* trans, const Id& parent_id);
-  Id GetLastChildId(BaseTransaction* trans, const Id& parent_id);
+  // Find the first child in the positional ordering under a parent,
+  // and fill in |*first_child_id| with its id.  Fills in a root Id if
+  // parent has no children.  Returns true if the first child was
+  // successfully found, or false if an error was encountered.
+  bool GetFirstChildId(BaseTransaction* trans, const Id& parent_id,
+                       Id* first_child_id) WARN_UNUSED_RESULT;
+
+  // Find the last child in the positional ordering under a parent,
+  // and fill in |*first_child_id| with its id.  Fills in a root Id if
+  // parent has no children.  Returns true if the first child was
+  // successfully found, or false if an error was encountered.
+  bool GetLastChildIdForTest(BaseTransaction* trans, const Id& parent_id,
+                             Id* last_child_id) WARN_UNUSED_RESULT;
 
   // Compute a local predecessor position for |update_item|.  The position
   // is determined by the SERVER_POSITION_IN_PARENT value of |update_item|,
   // as well as the SERVER_POSITION_IN_PARENT values of any up-to-date
   // children of |parent_id|.
   Id ComputePrevIdFromServerPosition(
       const EntryKernel* update_item,
       const syncable::Id& parent_id);
 
   // SaveChanges works by taking a consistent snapshot of the current Directory
@@ skipping 205 matching lines @@
   // children of |parent_id| in the kernel's parent_id_child_index.
   ParentIdChildIndex::iterator GetParentChildIndexUpperBound(
       const ScopedKernelLock& lock,
       const Id& parent_id);
 
   // Append the handles of the children of |parent_id| to |result|.
   void AppendChildHandles(
       const ScopedKernelLock& lock,
       const Id& parent_id, Directory::ChildHandles* result);
 
-  // Returns a pointer to what is probably (but not certainly) the
+  // Return a pointer to what is probably (but not certainly) the
   // first child of |parent_id|, or NULL if |parent_id| definitely has
   // no children.
   EntryKernel* GetPossibleFirstChild(
       const ScopedKernelLock& lock, const Id& parent_id);
 
+  // Return a pointer to what is probably (but not certainly) the last
+  // child of |parent_id|, or NULL if |parent_id| definitely has no
+  // children.
+  EntryKernel* GetPossibleLastChildForTest(
+      const ScopedKernelLock& lock, const Id& parent_id);
+
   Kernel* kernel_;
 
   DirectoryBackingStore* store_;
 };
 
 class ScopedKernelLock {
  public:
   explicit ScopedKernelLock(const Directory*);
   ~ScopedKernelLock() {}
 
@@ skipping 85 matching lines @@
 bool IsLegalNewParent(BaseTransaction* trans, const Id& id, const Id& parentid);
 
 // This function sets only the flags needed to get this entry to sync.
 void MarkForSyncing(syncable::MutableEntry* e);
 
 }  // namespace syncable
 
 std::ostream& operator <<(std::ostream&, const syncable::Blob&);
 
 #endif  // CHROME_BROWSER_SYNC_SYNCABLE_SYNCABLE_H_