Build Android's MessagePumpForUI by upstreaming SystemMessageHandler

base/android/java/org/chromium/base/SystemMessageHandler.java

Index: base/android/java/org/chromium/base/SystemMessageHandler.java
diff --git a/base/android/java/org/chromium/base/SystemMessageHandler.java b/base/android/java/org/chromium/base/SystemMessageHandler.java
new file mode 100644
index 0000000000000000000000000000000000000000..f7bb19f19e4e322c8dec3f281263368a2ece3983
--- /dev/null
+++ b/base/android/java/org/chromium/base/SystemMessageHandler.java
@@ -0,0 +1,93 @@
+// Copyright (c) 2012 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.Handler;
+import android.os.Message;
+import android.os.SystemClock;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+
+class SystemMessageHandler extends Handler {
+
+    private static final int TIMER_MESSAGE = 1;
+    private static final int DELAYED_TIMER_MESSAGE = 2;
+
+    // Native class pointer set by the constructor of the SharedClient native class.
+    private int mMessagePumpDelegateNative = 0;
+
+    // Used to ensure we have at most one TIMER_MESSAGE pending at once.
+    private AtomicBoolean mTimerFired = new AtomicBoolean(true);
+
+    // Used to insert TIMER_MESSAGE on the front of the system message queue during startup only.
+    // This is a wee hack, to give a priority boost to native tasks during startup as they tend to
+    // be on the critical path. (After startup, handling the UI with minimum latency is more
+    // important).
+    private boolean mStartupComplete = false;
+    private final long mStartupCompleteTime = System.currentTimeMillis() + 2000;
+    private final boolean startupComplete() {
+        if (!mStartupComplete && System.currentTimeMillis() > mStartupCompleteTime) {
+            mStartupComplete = true;
+        }
+        return mStartupComplete;
+    }
+
+    private SystemMessageHandler(int messagePumpDelegateNative) {
+        mMessagePumpDelegateNative = messagePumpDelegateNative;
+    }
+
+    @Override
+    public void handleMessage(Message msg) {
+        if (msg.what == TIMER_MESSAGE) {
+            mTimerFired.set(true);
+        }
+        while (nativeDoRunLoopOnce(mMessagePumpDelegateNative)) {
+            if (startupComplete()) {
+                setTimer();
+                break;
+            }
+        }
+    }
+
+    @CalledByNative
+    private void setTimer() {
+        if (!mTimerFired.getAndSet(false)) {
+            // mTimerFired was already false.
+            return;
+        }
+        if (startupComplete()) {
+            sendEmptyMessage(TIMER_MESSAGE);
+        } else {
+            sendMessageAtFrontOfQueue(obtainMessage(TIMER_MESSAGE));
+        }
+    }
+
+    // If millis <=0, it'll send a TIMER_MESSAGE instead of
+    // a DELAYED_TIMER_MESSAGE.
+    @SuppressWarnings("unused")
+    @CalledByNative
+    private void setDelayedTimer(long millis) {
+        if (millis <= 0) {
+            setTimer();
+        } else {
+            removeMessages(DELAYED_TIMER_MESSAGE);
+            sendEmptyMessageDelayed(DELAYED_TIMER_MESSAGE, millis);
+        }
+    }
+
+    @SuppressWarnings("unused")
+    @CalledByNative
+    private void removeTimer() {
+        removeMessages(TIMER_MESSAGE);
+        removeMessages(DELAYED_TIMER_MESSAGE);
+    }
+
+    @CalledByNative
+    private static SystemMessageHandler create(int messagePumpDelegateNative) {
+        return new SystemMessageHandler(messagePumpDelegateNative);
+    }
+
+    private native boolean nativeDoRunLoopOnce(int messagePumpDelegateNative);
+}