Move migration code out of WebDatabase and into table-specific classes.

chrome/browser/webdata/keyword_table.h

Index: chrome/browser/webdata/keyword_table.h
diff --git a/chrome/browser/webdata/keyword_table.h b/chrome/browser/webdata/keyword_table.h
index feae019a2caedd0276c061e96386793bdba4ddf1..fc31433858468f7616394eca6b36aec9d162253d 100644
--- a/chrome/browser/webdata/keyword_table.h
+++ b/chrome/browser/webdata/keyword_table.h
@@ -81,6 +81,13 @@ class KeywordTable : public WebDatabaseTable {
   bool SetBuitinKeywordVersion(int version);
   int GetBuitinKeywordVersion();
 
+  // Table migration functions.
+  bool MigrateToVersion21AutoGenerateKeywordColumn();
+  bool MigrateToVersion25AddLogoIDColumn();
+  bool MigrateToVersion26AddCreatedByPolicyColumn();
+  bool MigrateToVersion28SupportsInstantColumn();
+  bool MigrateToVersion29InstantUrlToSupportsInstant();
+
  private:
   DISALLOW_COPY_AND_ASSIGN(KeywordTable);
 };