MDL-37286 add new combined_progress_trace

This type of trace should be useful when multiple trace outputs requested.

lib/tests/weblib_test.php

@@ -297,4 +297,24 @@ class web_testcase extends advanced_testcase {
         $trace->reset_buffer();
         $this->assertSame('', $trace->get_buffer());
     }
+
+    public function test_combined_progres_trace() {
+        $this->resetAfterTest(false);
+
+        $trace1 = new progress_trace_buffer(new html_progress_trace(), false);
+        $trace2 = new progress_trace_buffer(new text_progress_trace(), false);
+
+        $trace = new combined_progress_trace(array($trace1, $trace2));
+
+        ob_start();
+        $trace->output('do');
+        $trace->output('re', 1);
+        $trace->output('mi', 2);
+        $trace->finished();
+        $output = ob_get_contents();
+        ob_end_clean();
+        $this->assertSame('', $output);
+        $this->assertSame("<p>do</p>\n<p>&#160;&#160;re</p>\n<p>&#160;&#160;&#160;&#160;mi</p>\n", $trace1->get_buffer());
+        $this->assertSame("do\n  re\n    mi\n", $trace2->get_buffer());
+    }
 }

lib/weblib.php

@@ -3297,7 +3297,7 @@ class error_log_progress_trace extends progress_trace {
 }
 
 /**
- * Special type of traced that can be used for catching of
+ * Special type of trace that can be used for catching of
  * output of other traces.
  *
  * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
@@ -3371,6 +3371,45 @@ class progress_trace_buffer extends progress_trace {
     }
 }
 
+/**
+ * Special type of trace that can be used for redirecting to multiple
+ * other traces.
+ *
+ * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ * @package moodlecore
+ */
+class combined_progress_trace extends progress_trace {
+    protected $traces;
+
+    /**
+     * @param array $traces multiple traces
+     */
+    public function __construct(array $traces) {
+        $this->traces = $traces;
+    }
+
+    /**
+     * Output an progress message in whatever format.
+     *
+     * @param string $message the message to output.
+     * @param integer $depth indent depth for this message.
+     */
+    public function output($message, $depth = 0) {
+        foreach($this->traces as $trace) {
+            $trace->output($message, $depth);
+        }
+    }
+
+    /**
+     * Called when the processing is finished.
+     */
+    public function finished() {
+        foreach($this->traces as $trace) {
+            $trace->finished();
+        }
+    }
+}
+
 /**
  * Returns a localized sentence in the current language summarizing the current password policy
  *