Add functionality to prune old crash reports from the database.

client/crash_report_database.h

Index: client/crash_report_database.h
diff --git a/client/crash_report_database.h b/client/crash_report_database.h
index baf95adcd335fce906b4c5b0f312210c561a11ed..1073d053debd02d988288e1efecf25c193594771 100644
--- a/client/crash_report_database.h
+++ b/client/crash_report_database.h
@@ -300,6 +300,13 @@ class CrashReportDatabase {
   //! \return The operation status code.
   virtual OperationStatus SkipReportUpload(const UUID& uuid) = 0;
 
+  //! \brief Deletes a crash report file and its associated metadata.
+  //!
+  //! \param[in] uuid The UUID of the report to delete.
+  //!
+  //! \return The operation status code.
+  virtual OperationStatus DeleteReport(const UUID& uuid) = 0;
+
  protected:
   CrashReportDatabase() {}