Add webview flag for PMProcessPriorityPolicy

Bug: 1077217
Change-Id: I1cee83b372ac8c0166e1d58006d5350a18439764
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5017277
Reviewed-by: Francois Pierre Doray <fdoray@chromium.org>
Commit-Queue: Francois Pierre Doray <fdoray@chromium.org>
Auto-Submit: Patrick Monette <pmonette@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1222526}

android_webview/java/src/org/chromium/android_webview/common/ProductionSupportedFlagList.java

@@ -773,7 +773,11 @@ private ProductionSupportedFlagList() {}
         Flag.baseFeature("V8MinorMS"),
         Flag.baseFeature(
                 AwFeatures.WEBVIEW_INJECT_PLATFORM_JS_APIS,
-                "Inject platform-specific Javascript APIs.")
+                "Inject platform-specific Javascript APIs."),
+        Flag.baseFeature(
+                "PMProcessPriorityPolicy",
+                "Controls whether the priority of renderers is controlled by the performance "
+                        + "manager."),
         // Add new commandline switches and features above. The final entry should have a
         // trailing comma for cleaner diffs.
     };