Add ANR/Watchdog subject to trace.

Test: Manual.
Bug: b/184939999

Change-Id: Iaaf378276cad42eea881ffeecbf1964a69d268fe

services/core/java/com/android/server/Watchdog.java

@@ -685,6 +685,7 @@ public class Watchdog {
             final UUID errorId = mTraceErrorLogger.generateErrorId();
             if (mTraceErrorLogger.isAddErrorIdEnabled()) {
                 mTraceErrorLogger.addErrorIdToTrace("system_server", errorId);
+                mTraceErrorLogger.addSubjectToTrace(subject, errorId);
             }
 
             // Log the atom as early as possible since it is used as a mechanism to trigger

services/core/java/com/android/server/am/ProcessErrorStateRecord.java

@@ -286,6 +286,7 @@ class ProcessErrorStateRecord {
                     && mService.mTraceErrorLogger.isAddErrorIdEnabled()) {
                 errorId = mService.mTraceErrorLogger.generateErrorId();
                 mService.mTraceErrorLogger.addErrorIdToTrace(mApp.processName, errorId);
+                mService.mTraceErrorLogger.addSubjectToTrace(annotation, errorId);
             } else {
                 errorId = null;
             }

services/core/java/com/android/server/am/TraceErrorLogger.java

@@ -54,4 +54,17 @@ public class TraceErrorLogger {
                 COUNTER_PREFIX + processName + "#" + errorId.toString(),
                 PLACEHOLDER_VALUE);
     }
+
+    /**
+     * Pushes a counter containing an ANR/Watchdog subject and a unique id so that the subject
+     * can be uniquely identified.
+     *
+     * @param subject The subject to include in the trace.
+     * @param errorId The unique id with which to tag the trace.
+     */
+    public void addSubjectToTrace(String subject, UUID errorId) {
+        Trace.traceCounter(Trace.TRACE_TAG_ACTIVITY_MANAGER,
+                String.format("Subject(for ErrorId %s):%s", errorId.toString(), subject),
+                PLACEHOLDER_VALUE);
+    }
 }