SimpleCache: Align fieldtrial_testing_config.json with more experimen…

…t values.

R=asvitkine

Bug: 913107
Change-Id: Ib6c1456f72a41bd2fa107d3ae6c8134707e17cf9
Reviewed-on: https://chromium-review.googlesource.com/c/1470650
Commit-Queue: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631737}

testing/variations/fieldtrial_testing_config.json

@@ -4533,8 +4533,7 @@
                     "name": "PrefetchTrailerHint2",
                     "params": {
                         "FullPrefetchBytes": "0",
-                        "TrailerPrefetchHint": "true",
-                        "TrailerPrefetchSpeculativeBytes": "0"
+                        "TrailerPrefetchHint": "true"
                     },
                     "enable_features": [
                         "SimpleCachePrefetchExperiment2"
@@ -4554,11 +4553,13 @@
                     "name": "ExperimentNoTrailerPrefetchHint4",
                     "params": {
                         "FullPrefetchBytes": "0",
-                        "TrailerPrefetchInt": "true",
-                        "TrailerPrefetchSpeculativeBytes": "0"
+                        "TrailerPrefetchHint": "true"
                     },
                     "enable_features": [
                         "SimpleCachePrefetchExperiment2"
+                    ],
+                    "disable_features": [
+                        "HttpCacheForceBackend"
                     ]
                 }
             ]