Bug 1518999 - Use the same conversion for Chrome and Firefox for FCP r=sparky,perftest-reviewers

Since this bug, Firefox will start to use the same conversion as
Chrome for reporting FCP. This patch cleans our code a little bit
to adapt that.

Differential Revision: https://phabricator.services.mozilla.com/D90109

testing/raptor/raptor/results.py

@@ -412,15 +412,11 @@ class BrowsertimeResultsHandler(PerftestResultsHandler):
         # bt to raptor names
         conversion = (
             ("fnbpaint", "firstPaint"),
-            ("fcp", "timeToContentfulPaint"),
+            ("fcp", ["paintTiming", "first-contentful-paint"]),
             ("dcf", "timeToDomContentFlushed"),
             ("loadtime", "loadEventEnd"),
         )
 
-        chrome_raptor_conversion = {
-            "timeToContentfulPaint": ["paintTiming", "first-contentful-paint"]
-        }
-
         def _get_raptor_val(mdict, mname, retval=False):
             # gets the measurement requested, returns the value
             # if one was found, or retval if it couldn't be found
@@ -544,12 +540,13 @@ class BrowsertimeResultsHandler(PerftestResultsHandler):
                     if self.app and "fennec" in self.app.lower() and bt == "fcp":
                         continue
 
-                    # chrome currently uses different names (and locations) for some metrics
-                    if raptor in chrome_raptor_conversion and _get_raptor_val(
+                    # FCP uses a different path to get the timing, so we need to do
+                    # some checks here
+                    if bt == "fcp" and not _get_raptor_val(
                         raw_result["browserScripts"][0]["timings"],
-                        chrome_raptor_conversion[raptor],
+                        raptor,
                     ):
-                        raptor = chrome_raptor_conversion[raptor]
+                        continue
 
                     # XXX looping several times in the list, could do better
                     for cycle in raw_result["browserScripts"]: