Don't crash when trying to create an ExtensionSyncData from invalid SyncData.

chrome/browser/extensions/app_sync_data.h

Index: chrome/browser/extensions/app_sync_data.h
diff --git a/chrome/browser/extensions/app_sync_data.h b/chrome/browser/extensions/app_sync_data.h
index bdbb1641f3608d4491f87f45eb4b24bc7743e3dd..efa0f649962bba5b6d41e1d5a856d2b02bcd8942 100644
--- a/chrome/browser/extensions/app_sync_data.h
+++ b/chrome/browser/extensions/app_sync_data.h
@@ -5,6 +5,7 @@
 #ifndef CHROME_BROWSER_EXTENSIONS_APP_SYNC_DATA_H_
 #define CHROME_BROWSER_EXTENSIONS_APP_SYNC_DATA_H_
 
+#include "base/memory/scoped_ptr.h"
 #include "chrome/browser/extensions/extension_sync_data.h"
 #include "extensions/common/constants.h"
 #include "sync/api/string_ordinal.h"
@@ -28,8 +29,6 @@ class ExtensionSyncData;
 class AppSyncData {
  public:
   AppSyncData();
-  explicit AppSyncData(const syncer::SyncData& sync_data);
-  explicit AppSyncData(const syncer::SyncChange& sync_change);
   AppSyncData(const Extension& extension,
               bool enabled,
               bool incognito_enabled,
@@ -40,6 +39,12 @@ class AppSyncData {
               extensions::LaunchType launch_type);
   ~AppSyncData();
 
+  // For constructing an AppSyncData from received sync data.

[not at google - send to devlin, 2015/03/11 23:21:34]

Mention these may be null (because...)

[Yoyo Zhou, 2015/03/12 00:25:48]

Ok. Also changed to not use the implicit constructor from null.

+  static scoped_ptr<AppSyncData> CreateFromSyncData(
+      const syncer::SyncData& sync_data);
+  static scoped_ptr<AppSyncData> CreateFromSyncChange(
+      const syncer::SyncChange& sync_change);
+
   // Retrive sync data from this class.
   syncer::SyncData GetSyncData() const;
   syncer::SyncChange GetSyncChange(
@@ -80,10 +85,10 @@ class AppSyncData {
   // Convert an AppSyncData back out to a sync structure.
   void PopulateAppSpecifics(sync_pb::AppSpecifics* specifics) const;
 
-  // Populate this class from sync inputs.
-  void PopulateFromAppSpecifics(
-      const sync_pb::AppSpecifics& specifics);
-  void PopulateFromSyncData(const syncer::SyncData& sync_data);
+  // Populate this class from sync inputs. Return true if the input
+  // was valid.
+  bool PopulateFromAppSpecifics(const sync_pb::AppSpecifics& specifics);
+  bool PopulateFromSyncData(const syncer::SyncData& sync_data);
 
   ExtensionSyncData extension_sync_data_;
   syncer::StringOrdinal app_launch_ordinal_;
@@ -97,4 +102,3 @@ class AppSyncData {
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_APP_SYNC_DATA_H_
-