DialogSurfaceManager implementation.

content/public/android/java/src/org/chromium/content/browser/androidoverlay/AndroidOverlayProviderImpl.java

+// Copyright 2017 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.content.browser.androidoverlay;
+
+import android.content.Context;
+import android.os.Handler;
+import android.os.HandlerThread;
+import android.os.IBinder;
+
+import org.chromium.base.ContextUtils;
+import org.chromium.base.annotations.CalledByNative;
+import org.chromium.media.IAndroidOverlay;
+import org.chromium.media.IAndroidOverlayCallback;
+import org.chromium.media.IAndroidOverlayProvider;
+
+/**
+ * Singleton class to create and manage AndroidOverlay.  Normally, you won't need
+ * to access this directly.  Instead, see the native wrappers in
+ * dialog_surface_manager.cc for usage.
+ *
+ * The wrappers do roughly the following on the gpu side:
+ *  - Create an IAndroidOverlayCallback.  For native, AndroidOverlayCallback hides
+ *    the threading issues and provides the java peer.
+ *  - Get an IAndroidOverlayManager from the browser via ChildProcessCallback .
+ *  - dialogSurface = IAndroidOverlayManager.createOverlay(callback)
+ *    This calls into the browser, and returns an IAndroidOverlay IBinder.
+ *  - Wrap the AndroidOverlay in a AndroidOverlayWrapper.  This provides the JNI
+ *    bindings for native.
+ *  - Expect callbacks on the callback to let you know when the underlying
+ *    android surface state changes.
+ *  - Use the surface.
+ *  - Call IAndroidOverlay::release() to destroy the surface when done.
+ */
+public class AndroidOverlayProviderImpl extends IAndroidOverlayProvider.Stub {
+    private static final String TAG = "AOProviderImpl";
+    private static AndroidOverlayProviderImpl sInstance;
+    private static final Object sLock = new Object();
+
+    private final Context mContext;
+
+    // We maintain a thread with a Looper for the AndroidOverlays to use,
+    // since Dialog requires one.  We don't want this to be the native thread
+    // that's used to create them, because it probably also has a native message
+    // loop.  Including a looper on it is not a good idea.  We don't want to use
+    // the UI thread, since it will process synchronous callbacks from Android.
+    private final Object mLock = new Object();
+    private HandlerThread mThread;
+    private Handler mHandler;
+
+    // Number of AndroidOverlays that have been created but not released.
+    private int mNumOverlays;
+
+    // Maximum number of concurrent surfaces we allow.
+    private static final int MAX_SURFACES = 1;
+
+    private AndroidOverlayProviderImpl() {
+        mContext = ContextUtils.getApplicationContext();
+        mNumOverlays = 0;
+    }
+
+    // Return the singleton instance, as a convenience.
+    public static IBinder getInstance() {
+        synchronized (sLock) {
+            if (sInstance == null) sInstance = new AndroidOverlayProviderImpl();
+
+            return sInstance.asBinder();
+        }
+    }
+
+    @Override
+    @CalledByNative

[boliu, 2017/02/08 00:01:58]

not needed, this doesn't generate jni headers

+    public IAndroidOverlay createOverlay(int rendererPid, int renderFrameId,
+            IAndroidOverlayCallback callback, int x, int y, int width, int height) {
+        // Note that we may be called on any random binder thread, so lock.
+        synchronized (mLock) {
+            // Limit the number of concurrent surfaces.
+            if (mNumOverlays >= MAX_SURFACES) return null;
+
+            startThreadIfNeededLocked();
+
+            mNumOverlays++;
+        }
+
+        return new DialogAndroidOverlay(rendererPid, renderFrameId, mContext, this, mHandler,
+                callback, x, y, width, height);
+    }
+
+    /**
+     * Called by AndroidOverlays when they no longer need the thread.
+     * Called on some random thread.
+     */
+    public void notifyReleased() {
+        synchronized (mLock) {
+            assert mNumOverlays > 0;
+            mNumOverlays--;
+
+            // We don't stop the looper thread here, else android can get mad when
+            // it tries to send a message from the dialog on this thread.
+            // AndroidOverlay might have to notify us separately to tell us
+            // when it's done with the thread, if we don't want to wait until then
+            // to start creating a new SV.
+            // Instead, we just avoid shutting down the thread at all for now.
+        }
+    }
+
+    /**
+     * Make sure that mThread and mHandler are ready for use.  Do nothing if
+     * they already are.
+     */
+    private void startThreadIfNeededLocked() {
+        // Called with mLock held only.

[boliu, 2017/02/08 00:01:58]

synhronized blocks are re-entrant safe, so rather than a comment and hoping
caller remembers, could just add synchronized block here as well

+        if (mThread != null) return;
+
+        mThread = new HandlerThread("AndroidOverlayThread");
+        mThread.start();
+        mHandler = new Handler(mThread.getLooper());
+    }
+}