Add @TargetApi to version dependent methods.

chrome/android/java/src/org/chromium/chrome/browser/multiwindow/MultiWindowUtils.java

Index: chrome/android/java/src/org/chromium/chrome/browser/multiwindow/MultiWindowUtils.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/multiwindow/MultiWindowUtils.java b/chrome/android/java/src/org/chromium/chrome/browser/multiwindow/MultiWindowUtils.java
index 86735622131177e74db192552d956d68b22b676e..6f1bbfcfd67de0d7cf78f6b87a460248f2ad19c9 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/multiwindow/MultiWindowUtils.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/multiwindow/MultiWindowUtils.java
@@ -242,6 +242,7 @@ public class MultiWindowUtils implements ActivityStateListener {
      * @return True if the Activity still has a task in Android recents, regardless of whether
      *         the Activity has been destroyed.
      */
+    @TargetApi(Build.VERSION_CODES.M)
     private boolean isActivityTaskInRecents(String className, Context context) {
         ActivityManager activityManager = (ActivityManager)
                 context.getSystemService(Context.ACTIVITY_SERVICE);