fix(@angular/cli): remove double console logs with different reporters

see the issue for details

closes #9528

Author: shairez

Diff for: packages/@angular/cli/plugins/karma.ts

@@ -247,8 +247,23 @@ function requestBlocker() {
 }
 
 // Strip the server address and webpack scheme (webpack://) from error log.
-const initSourcemapReporter: any = function (this: any, baseReporterDecorator: any) {
+const initSourcemapReporter: any = function (this: any, baseReporterDecorator: any, config: any) {
   baseReporterDecorator(this);
+
+  const reporterName = '@angular/cli';
+  const hasTrailingReporters = config.reporters.slice(-1).pop() !== reporterName;
+
+  // Copied from "karma-jasmine-diff-reporter" source code:
+  // In case, when multiple reporters are used in conjunction
+  // with initSourcemapReporter, they both will show repetitive log
+  // messages when displaying everything that supposed to write to terminal.
+  // So just suppress any logs from initSourcemapReporter by doing nothing on
+  // browser log, because it is an utility reporter,
+  // unless it's alone in the "reporters" option and base reporter is used.
+  if (hasTrailingReporters) {
+      this.writeCommonMsg = function () {};
+  }
+
   const urlRegexp = /\(http:\/\/localhost:\d+\/_karma_webpack_\/webpack:\//gi;
 
   this.onSpecComplete = function (_browser: any, result: any) {
@@ -260,7 +275,7 @@ const initSourcemapReporter: any = function (this: any, baseReporterDecorator: a
   };
 };
 
-initSourcemapReporter.$inject = ['baseReporterDecorator'];
+initSourcemapReporter.$inject = ['baseReporterDecorator', 'config'];
 
 module.exports = Object.assign({
   'framework:@angular/cli': ['factory', init],