Revert of Android: Add support for TraceEvent before the native library is loaded.

base/android/java/src/org/chromium/base/EarlyTraceEvent.java

-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-package org.chromium.base;
-
-import android.os.Process;
-import android.os.StrictMode;
-import android.os.SystemClock;
-
-import org.chromium.base.annotations.JNINamespace;
-import org.chromium.base.annotations.SuppressFBWarnings;
-
-import java.io.File;
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-
-/** Support for early tracing, before the native library is loaded.
- *
- * This is limited, as:
- * - Arguments are not supported
- * - Thread time is not reported
- * - Two events with the same name cannot be in progress at the same time.
- *
- * Events recorded here are buffered in Java until the native library is available. Then it waits
- * for the completion of pending events, and sends the events to the native side.
- *
- * Locking: This class is threadsafe. It is enabled when general tracing is, and then disabled when
- *          tracing is enabled from the native side. Event completions are still processed as long
- *          as some are pending, then early tracing is permanently disabled after dumping the
- *          events.  This means that if any early event is still pending when tracing is disabled,
- *          all early events are dropped.
- */
-@JNINamespace("base::android")
-public class EarlyTraceEvent {
-    // Must be kept in sync with the native kAndroidTraceConfigFile.
-    private static final String TRACE_CONFIG_FILENAME = "/data/local/chrome-trace-config.json";
-
-    /** Single trace event. */
-    @VisibleForTesting
-    static final class Event {
-        final String mName;
-        final int mThreadId;
-        final long mBeginTimeMs;
-        long mEndTimeMs;
-
-        Event(String name) {
-            mName = name;
-            mThreadId = Process.myTid();
-            mBeginTimeMs = SystemClock.elapsedRealtime();
-        }
-
-        void end() {
-            assert mEndTimeMs == 0;
-            mEndTimeMs = SystemClock.elapsedRealtime();
-        }
-    }
-
-    // State transitions are:
-    // - enable(): DISABLED -> ENABLED
-    // - disable(): ENABLED -> FINISHING
-    // - Once there are no pending events: FINISHING -> FINISHED.
-    @VisibleForTesting static final int STATE_DISABLED = 0;
-    @VisibleForTesting static final int STATE_ENABLED = 1;
-    @VisibleForTesting static final int STATE_FINISHING = 2;
-    @VisibleForTesting static final int STATE_FINISHED = 3;
-
-    // Locks the fields below.
-    private static final Object sLock = new Object();
-
-    @VisibleForTesting static volatile int sState = STATE_DISABLED;
-    // Not final as these object are not likely to be used at all.
-    @VisibleForTesting static List<Event> sCompletedEvents;
-    @VisibleForTesting static Map<String, Event> sPendingEvents;
-
-    /** @see TraceEvent#MaybeEnableEarlyTracing().
-     */
-    @SuppressFBWarnings("DMI_HARDCODED_ABSOLUTE_FILENAME")
-    static void maybeEnable() {
-        boolean shouldEnable = false;
-        // Checking for the trace config filename touches the disk.
-        StrictMode.ThreadPolicy oldPolicy = StrictMode.allowThreadDiskReads();
-        try {
-            CommandLine commandLine = CommandLine.getInstance();
-            if (commandLine != null && commandLine.hasSwitch("trace-startup")) {
-                shouldEnable = true;
-            } else {
-                try {
-                    shouldEnable = (new File(TRACE_CONFIG_FILENAME)).exists();
-                } catch (SecurityException e) {
-                    // Access denied, not enabled.
-                }
-            }
-        } finally {
-            StrictMode.setThreadPolicy(oldPolicy);
-        }
-        if (shouldEnable) enable();
-    }
-
-    @VisibleForTesting
-    static void enable() {
-        synchronized (sLock) {
-            if (sState != STATE_DISABLED) return;
-            sCompletedEvents = new ArrayList<Event>();
-            sPendingEvents = new HashMap<String, Event>();
-            sState = STATE_ENABLED;
-        }
-    }
-
-    /**
-     * Disables Early tracing.
-     *
-     * Once this is called, no new event will be registered. However, end() calls are still recorded
-     * as long as there are pending events. Once there are none left, pass the events to the native
-     * side.
-     */
-    static void disable() {
-        synchronized (sLock) {
-            if (sState != STATE_ENABLED) return;
-            sState = STATE_FINISHING;
-            maybeFinishLocked();
-        }
-    }
-
-    /** @see {@link TraceEvent#begin()}. */
-    public static void begin(String name) {
-        // begin() and end() are going to be called once per TraceEvent, this avoids entering a
-        // synchronized block at each and every call.
-        if (sState != STATE_ENABLED) return;
-        Event event = new Event(name);
-        Event conflictingEvent;
-        synchronized (sLock) {
-            if (sState != STATE_ENABLED) return;
-            conflictingEvent = sPendingEvents.put(name, event);
-        }
-        if (conflictingEvent != null) {
-            throw new IllegalArgumentException(
-                    "Multiple pending trace events can't have the same name");
-        }
-    }
-
-    /** @see {@link TraceEvent#end()}. */
-    public static void end(String name) {
-        int state = sState;
-        if (state != STATE_ENABLED && state != STATE_FINISHING) return;
-        synchronized (sLock) {
-            if (sState != STATE_ENABLED && sState != STATE_FINISHING) return;
-            Event event = sPendingEvents.remove(name);
-            if (event == null) return;
-            event.end();
-            sCompletedEvents.add(event);
-            if (sState == STATE_FINISHING) maybeFinishLocked();
-        }
-    }
-
-    private static void maybeFinishLocked() {
-        if (!sPendingEvents.isEmpty()) return;
-        sState = STATE_FINISHED;
-        dumpEvents(sCompletedEvents);
-        sCompletedEvents = null;
-        sPendingEvents = null;
-    }
-
-    private static void dumpEvents(List<Event> events) {
-        long nativeNowUs = nativeGetTimeTicksNowUs();
-        long javaNowUs = SystemClock.elapsedRealtime() * 1000;
-        long offsetMs = (nativeNowUs - javaNowUs) / 1000;
-        for (Event event : events) {
-            nativeRecordEarlyEvent(event.mName, event.mBeginTimeMs + offsetMs,
-                    event.mEndTimeMs + offsetMs, event.mThreadId);
-        }
-    }
-
-    private static native long nativeGetTimeTicksNowUs();
-    private static native void nativeRecordEarlyEvent(
-            String name, long beginTimeMs, long endTimeMs, int threadId);
-}