Auto merge of #19206 - asajeffrey:test-perf-add-differ-summary, r=aneeshusa

Add total time to test_differ in etc/ci/performance

<!-- Please describe your changes on the following line: -->

Add the total time to test_differ in etc/ci/performance.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes do not require tests because this is test infrastructure

<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/19206)
<!-- Reviewable:end -->

etc/ci/performance/test_differ.py

@@ -38,6 +38,18 @@ GREEN = '\033[92m'
 WARNING = '\033[93m'
 END = '\033[0m'
 
+
+total1 = 0
+total2 = 0
+
+
+def print_line(value1, value2, key):
+    diff = value2 - value1
+    change = diff / value1
+    color = BLUE if value1 <= value2 else GREEN
+    print("{}{:6} {:6} {:+6} {:+8.2%}   {}.{}".format(color, value1, value2, diff, change, key, END))
+
+
 for key in keys:
     value1 = data1.get(key)
     value2 = data2.get(key)
@@ -46,7 +58,10 @@ for key in keys:
     elif value2 and not(value1):
         print ("{}Test {}: missing from {}.{}".format(WARNING, key, args.file1, END))
     elif value1 and value2:
-        diff = value2 - value1
-        change = diff / value1
-        color = BLUE if value1 <= value2 else GREEN
-        print("{}{:6} {:6} {:+6} {:+8.2%}   {}.{}".format(color, value1, value2, diff, change, key, END))
+        total1 += value1
+        total2 += value2
+        print_line(value1, value2, key)
+
+
+print("")
+print_line(total1, total2, "TOTAL")