diff --git a/base/android/java/src/org/chromium/base/ThreadUtils.java b/base/android/java/src/org/chromium/base/ThreadUtils.java
index 8dfe3ea5d53475..d4fdbcf42a8227 100644
--- a/base/android/java/src/org/chromium/base/ThreadUtils.java
+++ b/base/android/java/src/org/chromium/base/ThreadUtils.java
@@ -12,7 +12,6 @@
 
 import org.chromium.base.task.PostTask;
 import org.chromium.base.task.TaskTraits;
-import org.chromium.build.BuildConfig;
 
 import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutionException;
@@ -33,8 +32,9 @@ public class ThreadUtils {
      * A helper object to ensure that interactions with a particular object only happens on a
      * particular thread.
      *
-     * <pre>Example:
-     *
+     * Example:
+     * <pre>
+     * {@code
      * class Foo {
      *     // Valid thread is set during construction here.
      *     private final ThreadChecker mThreadChecker = new ThreadChecker();
@@ -43,19 +43,11 @@ public class ThreadUtils {
      *         mThreadChecker.assertOnValidThread();
      *     }
      * }
+     * }
      * </pre>
      */
-    // TODO(b/274802355): Add @CheckDiscard once R8 can remove this.
     public static class ThreadChecker {
-        private long mThreadId;
-
-        public ThreadChecker() {
-            resetThreadId();
-        }
-
-        public void resetThreadId() {
-            mThreadId = BuildConfig.ENABLE_ASSERTS ? Process.myTid() : 0;
-        }
+        private final long mThreadId = Process.myTid();
 
         /**
          * Asserts that the current thread is the same as the one the ThreadChecker was constructed
diff --git a/base/android/java/src/org/chromium/base/jank_tracker/FrameMetricsStore.java b/base/android/java/src/org/chromium/base/jank_tracker/FrameMetricsStore.java
index f87d88edd414bb..e4e182cdb3d32b 100644
--- a/base/android/java/src/org/chromium/base/jank_tracker/FrameMetricsStore.java
+++ b/base/android/java/src/org/chromium/base/jank_tracker/FrameMetricsStore.java
@@ -18,7 +18,10 @@
  * This class stores relevant metrics from FrameMetrics between the calls to UMA reporting methods.
  */
 public class FrameMetricsStore {
-    private final ThreadChecker mThreadChecker = new ThreadChecker();
+    // FrameMetricsStore can only be accessed on the handler thread (from the
+    // JankReportingScheduler.getOrCreateHandler() method). However construction occurs on a
+    // separate thread so the ThreadChecker is instead constructed later.
+    private ThreadChecker mThreadChecker;
     // An arbitrary value from which to create a trace event async track. The only risk if this
     // clashes with another track is trace events will show up on both potentially looking weird in
     // the tracing UI. No other issue will occur.
@@ -85,10 +88,8 @@ public static String scenarioToString(@JankScenario.Type int scenario) {
      * checking.
      */
     void initialize() {
-        // FrameMetricsStore can only be accessed on the handler thread (from the
-        // JankReportingScheduler.getOrCreateHandler() method). However construction occurs on a
-        // separate thread so the ThreadChecker is instead constructed later.
-        mThreadChecker.resetThreadId();
+        assert mThreadChecker == null;
+        mThreadChecker = new ThreadChecker();
     }
 
     /** Records the total draw duration and jankiness for a single frame. */
diff --git a/base/android/proguard/chromium_code.flags b/base/android/proguard/chromium_code.flags
index e417fbaaa59eba..6393108051d330 100644
--- a/base/android/proguard/chromium_code.flags
+++ b/base/android/proguard/chromium_code.flags
@@ -43,11 +43,6 @@
   <init>();
 }
 
-# Required to remove fields until b/274802355 is resolved.
--assumevalues class !cr_allowunused,** {
-  final org.chromium.base.ThreadUtils$ThreadChecker * return _NONNULL_;
-}
-
 # TODO(agrieve): Remove once we start to use Android U SDK.
 -dontwarn android.window.BackEvent
 -dontwarn android.window.OnBackAnimationCallback
diff --git a/chrome/android/expectations/monochrome_64_32_public_bundle.proguard_flags.expected b/chrome/android/expectations/monochrome_64_32_public_bundle.proguard_flags.expected
index 24f6c31cedb671..c1e055cdb08d8b 100644
--- a/chrome/android/expectations/monochrome_64_32_public_bundle.proguard_flags.expected
+++ b/chrome/android/expectations/monochrome_64_32_public_bundle.proguard_flags.expected
@@ -252,11 +252,6 @@
   <init>();
 }
 
-# Required to remove fields until b/274802355 is resolved.
--assumevalues class !cr_allowunused,** {
-  final org.chromium.base.ThreadUtils$ThreadChecker * return _NONNULL_;
-}
-
 # TODO(agrieve): Remove once we start to use Android U SDK.
 -dontwarn android.window.BackEvent
 -dontwarn android.window.OnBackAnimationCallback
diff --git a/components/cronet/android/cronet_combined_impl_native_proguard_golden.cfg b/components/cronet/android/cronet_combined_impl_native_proguard_golden.cfg
index f2737579aa6853..11890807a5530d 100644
--- a/components/cronet/android/cronet_combined_impl_native_proguard_golden.cfg
+++ b/components/cronet/android/cronet_combined_impl_native_proguard_golden.cfg
@@ -44,11 +44,6 @@
   <init>();
 }
 
-# Required to remove fields until b/274802355 is resolved.
--assumevalues class !cr_allowunused,** {
-  final org.chromium.base.ThreadUtils$ThreadChecker * return _NONNULL_;
-}
-
 # TODO(agrieve): Remove once we start to use Android U SDK.
 -dontwarn android.window.BackEvent
 -dontwarn android.window.OnBackAnimationCallback