DO NOT MERGE: Revert Move startInput for WINDOW_FOCUS_GAIN to background thread

Reason for revert:
Caused an unexpected regression Bug 144174015

Bug: 139806621
Bug: 144103599
Fix: 144174015
Test: Manually verified Bug 144174015 disappeared as follows
 1. Open Gmail then start composing an email
 2. Swipe up the home button to recents then re-launch Gmail
 3. Do the step 2 several times.
 4. Make sure that you can still type something on Gmail.
Change-Id: I9265f01ed2f6e4aca7728d278f06ceea5633dac5

core/java/android/view/inputmethod/InputMethodManager.java

@@ -92,10 +92,7 @@ import java.util.Comparator;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
-import java.util.concurrent.CancellationException;
-import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CountDownLatch;
-import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
 
 /**
@@ -424,13 +421,6 @@ public final class InputMethodManager {
     int mCursorCandStart;
     int mCursorCandEnd;
 
-    /**
-     * Initial startInput with {@link StartInputReason.WINDOW_FOCUS_GAIN} is executed
-     * in a background thread. Later, if there is an actual startInput it will wait on
-     * main thread till the background thread completes.
-     */
-    private CompletableFuture<Void> mWindowFocusGainFuture;
-
     /**
      * The instance that has previously been sent to the input method.
      */
@@ -1608,18 +1598,6 @@ public final class InputMethodManager {
     boolean startInputInner(@StartInputReason int startInputReason,
             @Nullable IBinder windowGainingFocus, @StartInputFlags int startInputFlags,
             @SoftInputModeFlags int softInputMode, int windowFlags) {
-        if (startInputReason != StartInputReason.WINDOW_FOCUS_GAIN
-                && mWindowFocusGainFuture != null) {
-            try {
-                mWindowFocusGainFuture.get();
-            } catch (ExecutionException | InterruptedException e) {
-                // do nothing
-            } catch (CancellationException e) {
-                // window no longer has focus.
-                return true;
-            }
-        }
-
         final View view;
         synchronized (mH) {
             view = mServedView;
@@ -1973,38 +1951,31 @@ public final class InputMethodManager {
             startInputFlags |= StartInputFlags.FIRST_WINDOW_FOCUS_GAIN;
         }
 
-        final boolean forceNewFocus1 = forceNewFocus;
+        if (checkFocusNoStartInput(forceNewFocus)) {
-        final int startInputFlags1 = startInputFlags;
+            // We need to restart input on the current focus view.  This
-        if (mWindowFocusGainFuture != null) {
+            // should be done in conjunction with telling the system service
-            mWindowFocusGainFuture.cancel(false/* mayInterruptIfRunning */);
+            // about the window gaining focus, to help make the transition
+            // smooth.
+            if (startInputInner(StartInputReason.WINDOW_FOCUS_GAIN, rootView.getWindowToken(),
+                    startInputFlags, softInputMode, windowFlags)) {
+                return;
+            }
         }
-        mWindowFocusGainFuture = CompletableFuture.runAsync(() -> {
-            if (checkFocusNoStartInput(forceNewFocus1)) {
-                // We need to restart input on the current focus view.  This
-                // should be done in conjunction with telling the system service
-                // about the window gaining focus, to help make the transition
-                // smooth.
-                if (startInputInner(StartInputReason.WINDOW_FOCUS_GAIN, rootView.getWindowToken(),
-                        startInputFlags1, softInputMode, windowFlags)) {
-                    return;
-                }
-            }
 
-            // For some reason we didn't do a startInput + windowFocusGain, so
+        // For some reason we didn't do a startInput + windowFocusGain, so
-            // we'll just do a window focus gain and call it a day.
+        // we'll just do a window focus gain and call it a day.
-            synchronized (mH) {
+        synchronized (mH) {
-                try {
+            try {
-                    if (DEBUG) Log.v(TAG, "Reporting focus gain, without startInput");
+                if (DEBUG) Log.v(TAG, "Reporting focus gain, without startInput");
-                    mService.startInputOrWindowGainedFocus(
+                mService.startInputOrWindowGainedFocus(
-                            StartInputReason.WINDOW_FOCUS_GAIN_REPORT_ONLY, mClient,
+                        StartInputReason.WINDOW_FOCUS_GAIN_REPORT_ONLY, mClient,
-                            rootView.getWindowToken(), startInputFlags1, softInputMode, windowFlags,
+                        rootView.getWindowToken(), startInputFlags, softInputMode, windowFlags,
-                            null, null, 0 /* missingMethodFlags */,
+                        null, null, 0 /* missingMethodFlags */,
-                            rootView.getContext().getApplicationInfo().targetSdkVersion);
+                        rootView.getContext().getApplicationInfo().targetSdkVersion);
-                } catch (RemoteException e) {
+            } catch (RemoteException e) {
-                    throw e.rethrowFromSystemServer();
+                throw e.rethrowFromSystemServer();
-                }
             }
-        });
+        }
     }
 
     /** @hide */
@@ -2019,10 +1990,6 @@ public final class InputMethodManager {
                 // If the mCurRootView is losing window focus, release the strong reference to it
                 // so as not to prevent it from being garbage-collected.
                 mCurRootView = null;
-                if (mWindowFocusGainFuture != null) {
-                    mWindowFocusGainFuture.cancel(false /* mayInterruptIfRunning */);
-                    mWindowFocusGainFuture = null;
-                }
             } else {
                 if (DEBUG) {
                     Log.v(TAG, "Ignoring onPreWindowFocus()."