Reland Plumb trace canonicalUrl through TelemetryInfo.

tracing/tracing/metrics/metric_map_function_test.html

Index: tracing/tracing/metrics/metric_map_function_test.html
diff --git a/tracing/tracing/metrics/metric_map_function_test.html b/tracing/tracing/metrics/metric_map_function_test.html
index e449f4a0c83c179a7262b765ec4a8eaea678e928..2e74dbf9d7bbde3970903263f2debf36045392f0 100644
--- a/tracing/tracing/metrics/metric_map_function_test.html
+++ b/tracing/tracing/metrics/metric_map_function_test.html
@@ -80,5 +80,22 @@ tr.b.unittest.testSuite(function() {
     }, Error, 'Illegal diagnostic name ' +
         `"${tr.v.d.RESERVED_NAMES.GROUPING_PATH}" on Histogram "a"`);
   });
+
+  test('validateCanonicalUrl', function() {
+    const result = new tr.mre.MreResult();
+    const m = TestUtils.newModel(model => {
+      model.canonicalUrl = 'canonical url';
+      model.metadata = [{
+        value: {
+          telemetry: {
+            traceUrls: ['trace url'],
+          },
+        },
+      }];
+    });
+    assert.throw(function() {
+      tr.metrics.metricMapFunction(result, m, {metrics: ['sampleMetric']});
+    }, Error, 'canonicalUrl "canonical url" != traceUrl "trace url"');
+  });
 });
 </script>