More temporary mochitest hang diagnostics: kill the plugin process with SIGSEGV if it doesn't shut down within 30 seconds.

ipc/chromium/src/chrome/common/process_watcher_posix_sigchld.cc

@@ -122,14 +122,25 @@ protected:
 
 
 
-
+#if 0
     HANDLE_EINTR(waitpid(process_, NULL, 0));
+#else
 
+    const int maxWaits = 30;
+    int waits = 0;
+    while (!IsProcessDead(process_) && ++waits < maxWaits)
+      sleep(1);
 
-
-
-    printf("TEST-UNEXPECTED-FAIL | process %d done busy-waiting on | child process %d\n", getpid(), process_);
-
+    if (waits < maxWaits) {
+      printf("TEST-UNEXPECTED-FAIL | process %d done busy-waiting on | child process %d\n", getpid(), process_);
+    }
+    else {
+      printf("TEST-UNEXPECTED-FAIL | process %d wait on | child process %d timed out!\n", getpid(), process_);
+      // kill the child in such a way that breakpad is triggered
+      kill(process_, SIGSEGV);
+      HANDLE_EINTR(waitpid(process_, NULL, 0));
+    }
+#endif