Add DirectCompositionForceFullDamage to fieldtrial_testing_config.json.

BUG=1117185
TEST=bots

Change-Id: If904ab785166485812438a9bc2f2bedf16fec2aa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2525853
Auto-Submit: Zhenyao Mo <zmo@chromium.org>
Commit-Queue: Jesse Doherty <jwd@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#825809}

testing/variations/fieldtrial_testing_config.json

@@ -2219,6 +2219,21 @@
             ]
         }
     ],
+    "DirectCompositionForceFullDamage": [
+        {
+            "platforms": [
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "DirectCompositionForceFullDamage"
+                    ]
+                }
+            ]
+        }
+    ],
     "DirectCompositionSoftwareOverlays": [
         {
             "platforms": [