Introduce ThreadedInputConnection behind a switch

content/public/android/java/src/org/chromium/content/browser/input/ThreadedInputConnectionFactory.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.content.browser.input;
+
+import android.os.Handler;
+import android.os.HandlerThread;
+import android.view.View;
+import android.view.inputmethod.EditorInfo;
+
+import org.chromium.base.Log;
+
+/**
+ * Default factory for ChromiumBaseInputConnection classes.
+ */
+public class ThreadedInputConnectionFactory implements ChromiumBaseInputConnection.Factory {
+    private static final String TAG = "cr_Ime";
+    private static final boolean DEBUG_LOGS = false;
+
+    private ThreadedInputConnection mThreadedInputConnection;
+    private final Handler mHandler;
+    private final InputMethodManagerWrapper mInputMethodManagerWrapper;
+    private ThreadedInputConnectionProxyView mProxyView;
+
+    ThreadedInputConnectionFactory(InputMethodManagerWrapper inputMethodManagerWrapper) {
+        HandlerThread thread =
+                new HandlerThread("InputConnectionHandlerThread", HandlerThread.NORM_PRIORITY);
+        thread.start();
+        mHandler = new Handler(thread.getLooper());
+        mInputMethodManagerWrapper = inputMethodManagerWrapper;
+    }
+
+    private boolean isCalledFromProxyView() {
+        for (StackTraceElement ste : Thread.currentThread().getStackTrace()) {
+            String className = ste.getClassName();
+            if (className != null
+                    && className.contains(ThreadedInputConnectionProxyView.class.getName())) {

[Ted C, 2016/02/17 19:09:34]

What view is passed into initializeAndGet?   Is it always the container view?  
wondering if we can do an instanceof check instead of this.

[Changwan Ryu, 2016/02/18 06:03:27]

I think it should always be the container view.
The reason is that when an app overrides WebView as MyWebView and overrides
onCreateInputConnection(), their overridden function should be called, so
ProxyView should call ContainerView#onCreateInputConnection().

I could not find a better way to distinguish this.

+                return true;
+            }
+        }
+        return false;
+    }
+
+    @Override
+    public ChromiumBaseInputConnection initializeAndGet(
+            View view, ImeAdapter imeAdapter, int inputType, int inputFlags, EditorInfo outAttrs) {
+        ImeUtils.checkOnUiThread();
+        if (!isCalledFromProxyView()) {
+            if (DEBUG_LOGS) Log.w(TAG, "initializeAndGet: not called from proxy view");
+            triggerDelayedOnCreateInputConnection(view);
+            return null;
+        }
+        if (DEBUG_LOGS) Log.w(TAG, "initializeAndGet: called from proxy view");
+        if (mThreadedInputConnection == null) {
+            if (DEBUG_LOGS) Log.w(TAG, "Creating ThreadedInputConnection...");
+            mThreadedInputConnection = new ThreadedInputConnection(imeAdapter, mHandler);
+        }
+        mThreadedInputConnection.initializeOutAttrsOnUiThread(inputType, inputFlags, outAttrs);
+        return mThreadedInputConnection;
+    }
+
+    private void triggerDelayedOnCreateInputConnection(final View view) {
+        mProxyView = new ThreadedInputConnectionProxyView(view.getContext(), mHandler, view);
+        mProxyView.requestFocus();
+        view.getHandler().post(new Runnable() {
+            @Override
+            public void run() {
+                // This is a hack to make InputMethodManager believe that the proxy view
+                // now has a focus. As a result, InputMethodManager will think that mProxyView
+                // is focused, and will call getHandler() of the view when creating input
+                // connection.
+
+                // Step 1: Set InputMethodManager#mNextServedView as mProxyView.
+                mProxyView.onWindowFocusChanged(true);
+                // Step 2: Have InputMethodManager focus in on mNextServedView.
+                mInputMethodManagerWrapper.isActive(view);
+                // Step 3: Verify that the above hack worked.
+                mHandler.post(new Runnable() {
+                    @Override
+                    public void run() {
+                        ImeUtils.checkCondition(mInputMethodManagerWrapper.isActive(mProxyView));
+                        ImeUtils.checkCondition(mInputMethodManagerWrapper.isActive(view));
+                    }
+                });
+
+                // TODO(changwan): come up with fallback plan or crash when the above hack fails.

[Ted C, 2016/02/17 19:09:34]

we can't actually launch this until we have a solution for this BTW

[Changwan Ryu, 2016/02/18 06:03:27]

Agreed. I'm planning to do the following:
- disable command line flag
- raise assertion error
- log UMA for success & failure
- log UMA for usage of ThreadedInputConnection vs ReplicaInputConnection
(Ideally it would be awesome to disable command line flag only for the current
major version for iterations, but I could not find a way to do that.)

[Changwan Ryu, 2016/02/18 10:38:42]

Added code to fall back to ReplicaInputConnection. PTAL.

+            }
+        });
+    }
+
+    @Override
+    public Handler getHandler() {
+        return mHandler;
+    }
+}